feature #908 Simplify the log files by ignoring the "event" channel by default (javiereguiluz)

This PR was squashed before being merged into the 2.3 branch (closes #908).

Discussion
----------

Simplify the log files by ignoring the "event" channel by default

Imagine that you are a newcomer who installs Symfony. You browse the "Welcome Page" and everything seems to work fine:

![symfony_welcome_page](https://cloud.githubusercontent.com/assets/73419/11783046/3be7810c-a275-11e5-8bb5-5a9ab86e55f6.png)

But then, you open the `var/logs/dev.log` file and find this monstrosity:

```
[2015-12-14 15:05:08] event.DEBUG: Notified event "console.command" to listener "Symfony\Component\HttpKernel\EventListener\DebugHandlersListener::configure". [] []
[2015-12-14 15:05:08] event.DEBUG: Notified event "console.command" to listener "Symfony\Bridge\Monolog\Handler\ConsoleHandler::onCommand". [] []
[2015-12-14 15:05:08] event.DEBUG: Notified event "console.command" to listener "Symfony\Bridge\Monolog\Handler\ConsoleHandler::onCommand". [] []
[2015-12-14 15:05:12] request.INFO: Matched route "homepage". {"route_parameters":{"_controller":"AppBundle\\Controller\\DefaultController::indexAction","_route":"homepage"},"request_uri":"http://127.0.0.1:9000/"} []
[2015-12-14 15:05:12] security.INFO: Populated the TokenStorage with an anonymous Token. [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\DebugHandlersListener::configure". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\DumpListener::configure". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Bundle\FrameworkBundle\EventListener\SessionListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\FragmentListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\RouterListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\LocaleListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\TranslatorListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\Security\Http\Firewall::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Symfony\Bundle\FrameworkBundle\DataCollector\RouterDataCollector::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Symfony\Component\HttpKernel\DataCollector\RequestDataCollector::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\ControllerListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\ParamConverterListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\HttpCacheListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\SecurityListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\TemplateListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\Security\Http\RememberMe\ResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\HttpCacheListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Bundle\WebProfilerBundle\EventListener\WebDebugToolbarListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\SaveSessionListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\StreamedResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\LocaleListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\TranslatorListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\RouterListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\Security\Http\Firewall::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.terminate" to listener "Symfony\Bundle\SwiftmailerBundle\EventListener\EmailSenderListener::onTerminate". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.terminate" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelTerminate". [] []
[2015-12-14 15:05:12] request.INFO: Matched route "_wdt". {"route_parameters":{"_controller":"web_profiler.controller.profiler:toolbarAction","token":"41ff2e","_route":"_wdt"},"request_uri":"http://127.0.0.1:9000/_wdt/41ff2e"} []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\DebugHandlersListener::configure". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\DumpListener::configure". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Bundle\FrameworkBundle\EventListener\SessionListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\FragmentListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\RouterListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\LocaleListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\HttpKernel\EventListener\TranslatorListener::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.request" to listener "Symfony\Component\Security\Http\Firewall::onKernelRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Symfony\Bundle\FrameworkBundle\DataCollector\RouterDataCollector::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Symfony\Component\HttpKernel\DataCollector\RequestDataCollector::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\ControllerListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\ParamConverterListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\HttpCacheListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\SecurityListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.controller" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\TemplateListener::onKernelController". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\Security\Http\RememberMe\ResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Sensio\Bundle\FrameworkExtraBundle\EventListener\HttpCacheListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Bundle\WebProfilerBundle\EventListener\WebDebugToolbarListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\SaveSessionListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.response" to listener "Symfony\Component\HttpKernel\EventListener\StreamedResponseListener::onKernelResponse". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\LocaleListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\TranslatorListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\HttpKernel\EventListener\RouterListener::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.finish_request" to listener "Symfony\Component\Security\Http\Firewall::onKernelFinishRequest". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.terminate" to listener "Symfony\Bundle\SwiftmailerBundle\EventListener\EmailSenderListener::onTerminate". [] []
[2015-12-14 15:05:12] event.DEBUG: Notified event "kernel.terminate" to listener "Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelTerminate". [] []
```

62 log lines for just a simple page looks suspicious. And if you take a closer look, all the `event.DEBUG` lines looks useless. This makes you think that Symfony is bloated and complex.

However, if we ship the Standard Edition with the change proposed in this Pull Request, the same page will generate this beautifully concise log file:

```
[2015-12-14 15:07:08] request.INFO: Matched route "homepage". {"route_parameters":{"_controller":"AppBundle\\Controller\\DefaultController::indexAction","_route":"homepage"},"request_uri":"http://127.0.0.1:9000/"} []
[2015-12-14 15:07:08] security.INFO: Populated the TokenStorage with an anonymous Token. [] []
[2015-12-14 15:07:08] request.INFO: Matched route "_wdt". {"route_parameters":{"_controller":"web_profiler.controller.profiler:toolbarAction","token":"61580e","_route":"_wdt"},"request_uri":"http://127.0.0.1:9000/_wdt/61580e"} []
```

And even if I mentioned newcomers, most of the developers I know waste a lot of time trying to figure out the real log messages from all the "event logs noise".

Commits
-------

de6ecbb Simplify the log files by ignoring the "event" channel by default

Author: Tobion

app/config/config_dev.yml

@@ -14,9 +14,10 @@ web_profiler:
 monolog:
     handlers:
         main:
-            type:  stream
-            path:  "%kernel.logs_dir%/%kernel.environment%.log"
+            type: stream
+            path: "%kernel.logs_dir%/%kernel.environment%.log"
             level: debug
+            channels: [!event]
         firephp:
             type:  firephp
             level: info