Merge branch '3.4' into 4.0

* 3.4:
  removing h1 but making JS more fool-proof
  Make use of %kernel.project_dir% parameter
  Mention the handy `ignoreExtraKeys()` method
  add empty h1 tags to html template

Author: xabbuh

components/config/definition.rst

@@ -219,6 +219,9 @@ Before defining the children of an array node, you can provide options like:
     If called (with ``false``), keys with dashes are *not* normalized to underscores.
     It is recommended to use this with prototype nodes where the user will define
     a key-value map, to avoid an unnecessary transformation.
+``ignoreExtraKeys()``
+    Allows extra config keys to be specified under an array without
+    throwing an exception.
 
 A basic prototyped array configuration can be defined as follows::
 

configuration/override_dir_structure.rst

@@ -104,7 +104,7 @@ define your own templates directory (or directories):
         # app/config/config.yml
         twig:
             # ...
-            paths: ["%kernel.root_dir%/../templates"]
+            paths: ["%kernel.project_dir%/templates"]
 
     .. code-block:: xml
 
@@ -119,7 +119,7 @@ define your own templates directory (or directories):
                 http://symfony.com/schema/dic/twig/twig-1.0.xsd">
 
             <twig:config>
-                <twig:path>%kernel.root_dir%/../templates</twig:path>
+                <twig:path>%kernel.project_dir%/templates</twig:path>
             </twig:config>
 
         </container>
@@ -129,7 +129,7 @@ define your own templates directory (or directories):
         // app/config/config.php
         $container->loadFromExtension('twig', array(
             'paths' => array(
-                '%kernel.root_dir%/../templates',
+                '%kernel.project_dir%/templates',
             ),
         ));
 
@@ -197,7 +197,7 @@ You also need to change the ``extra.symfony-web-dir`` option in the
                     http://symfony.com/schema/dic/assetic/assetic-1.0.xsd">
 
                 <!-- ... -->
-                <assetic:config read-from="%kernel.root_dir%/../../public_html" />
+                <assetic:config read-from="%kernel.project_dir%/../public_html" />
 
             </container>
 

frontend/encore/simple-example.rst

@@ -144,7 +144,7 @@ Great! Use ``require()`` to import ``jquery`` and ``greet.js``:
     var greet = require('./greet');
 
     $(document).ready(function() {
-        $('h1').html(greet('john'));
+        $('body').prepend('<h1>'+greet('john')+'</h1>');
     });
 
 That's it! When you build your assets, jQuery and ``greet.js`` will automatically