Enabled APC cache for doctrine metadata & queries

Doctrine is never intended to be used in any live environment without metadata and query caching (note this is not result caching). Its performance will be significantly impeded without it

php-symfony2/app/config/config_prod.yml

@@ -11,11 +11,11 @@ framework:
     #validation:
     #    cache: apc
 
-#doctrine:
-#    orm:
-#        metadata_cache_driver: apc
+doctrine:
+    orm:
+        metadata_cache_driver: apc
 #        result_cache_driver: apc
-#        query_cache_driver: apc
+        query_cache_driver: apc
 
 monolog:
     handlers: