bug #4222 [Components][DependencyInjection] do not reference services in parameters (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Components][DependencyInjection] do not reference services in parameters

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4211

Commits
-------

4b10abf do not reference services in parameters

Author: weaverryan

components/dependency_injection/parameters.rst

@@ -336,76 +336,3 @@ To disable this behavior, use the ``string`` type:
 
     This is not available for YAML and PHP, because they already have built-in
     support for the PHP keywords.
-
-Syntax for Referencing Services
--------------------------------
-
-You can of course also reference services, which looks a bit different in
-each format. You can configure the behavior if the referenced service does
-not exist. By default, an exception is thrown when a non-existent service
-is referenced.
-
-YAML
-~~~~
-
-Start the string with  ``@`` or ``@?`` to reference a service in YAML.
-
-* ``@mailer`` references the ``mailer`` service. If the service does not
-  exist, an exception will be thrown;
-* ``@?mailer`` references the ``mailer`` service. If the service does not
-  exist, it will be ignored;
-
-.. code-block:: yaml
-
-    parameters:
-        # if 'my_mailer' service isn't defined, an exception will be raised
-        foo: @my_mailer
-
-        # if 'my_logger' service isn't defined, 'bar' will be null
-        bar: @?my_logger
-
-.. tip::
-
-    Use ``@@`` to escape the ``@`` symbol in YAML. ``@@mailer`` will be
-    converted into the string ``"@mailer"`` instead of referencing the
-    ``mailer`` service.
-
-XML
-~~~
-
-In XML, use the ``service`` type. The behavior if the service does not exist
-can be specified using the ``on-invalid`` argument. By default, an exception
-is thrown. Valid values for ``on-invalid`` are ``null`` (uses ``null`` in place
-of the missing service) or ``ignored`` (very similar, except if used on a
-method call, the method call is removed).
-
-.. code-block:: xml
-
-    <parameters>
-        <!-- if 'my_mailer' service isn't defined, an exception will be raised -->
-        <parameter key="foo" type="service" id="my_mailer" />
-
-        <!-- if 'my_logger' service isn't defined, 'bar' will be null -->
-        <parameter key="bar" type="service" id="my_logger" on-invalid="null" />
-    </parameters>
-
-PHP
-~~~
-
-In PHP, you can use the
-:class:`Symfony\\Component\\DependencyInjection\\Reference` class to reference
-a service. The invalid behavior is configured using the second constructor
-argument and constants from
-:class:`Symfony\\Component\\DependencyInjection\\ContainerInterface`.
-
-.. code-block:: php
-
-    use Symfony\Component\DependencyInjection\Reference;
-
-    // if 'my_mailer' service isn't defined, an exception will be raised
-    $container->setParameter('foo', new Reference('my_mailer'));
-
-    // if 'my_logger' service isn't defined, 'bar' will be null
-    $container->setParameter('bar', new Reference('my_logger',
-        ContainerInterface::NULL_ON_INVALID_REFERENCE
-    ));