enable phpXdebug by default for dev environment

the php development.ini has xdebug enabled by default, so xdebug should also be installed.
alternative: update the docs, that you have to enable phpXdebug first.

Author: fourty2

etc/application.development.yml

@@ -5,7 +5,7 @@ PROVISION:
 
   install:
     phpBlackfire:       false
-    phpXdebug:          false
+    phpXdebug:          true
     apacheModPagespeed: false
 
   service: