minor #3859 Add filter cssrewrite (DOEO)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes #3859).

Discussion
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Add filter cssrewrite

According to : http://symfony.com/doc/current/cookbook/assetic/asset_management.html#cookbook-assetic-cssrewrite

For keep link to image in CSS

Commits
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0210a35 Add filter cssrewrite

Author: weaverryan

cookbook/assetic/uglifyjs.rst

@@ -232,15 +232,16 @@ helper:
 
     .. code-block:: html+jinja
 
-        {% stylesheets '@AcmeFooBundle/Resources/public/css/*' filter='uglifycss' %}
+        {% stylesheets 'bundles/AcmeFoo/css/*' filter='uglifycss' filter='cssrewrite' %}
              <link rel="stylesheet" href="{{ asset_url }}" />
         {% endstylesheets %}
 
     .. code-block:: html+php
 
         <?php foreach ($view['assetic']->stylesheets(
-            array('@AcmeFooBundle/Resources/public/css/*'),
-            array('uglifycss')
+            array('bundles/AcmeFoo/css/*'),
+            array('uglifycss'),
+            array('cssrewrite')
         ) as $url): ?>
             <link rel="stylesheet" href="<?php echo $view->escape($url) ?>" />
         <?php endforeach; ?>