[WebBundle] Fixed import of base configuration in YAML skeleton.

src/Symfony/Framework/WebBundle/Resources/skeleton/application/yaml/config/config_dev.yml

@@ -1,5 +1,5 @@
 imports:
-  - { resource: config.xml }
+  - { resource: config.yml }
 
 zend.logger:
   priority: debug

src/Symfony/Framework/WebBundle/Resources/skeleton/application/yaml/config/config_prod.yml

@@ -1,2 +1,2 @@
 imports:
-  - { resource: config.xml }
+  - { resource: config.yml }