[DependencyInjection] added phpdoc for property $container in ContainerAware

This should ease code-completion a little bit...

src/Symfony/Component/DependencyInjection/ContainerAware.php

@@ -11,6 +11,8 @@
 
 namespace Symfony\Component\DependencyInjection;
 
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
 /**
  * A simple implementation of ContainerAwareInterface.
  *
@@ -18,6 +20,9 @@ namespace Symfony\Component\DependencyInjection;
  */
 class ContainerAware implements ContainerAwareInterface
 {
+    /**
+     * @var ContainerInterface
+     */
     protected $container;
 
     /**