Ability to assign issues to groups (#2964).

Option is disabled by default. It can be turned on in application settings.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@6306 e93f8b46-1217-0410-a6f0-8f06a7374b81

config/settings.yml

@@ -121,6 +121,8 @@ user_format:
   format: symbol
 cross_project_issue_relations:
   default: 0
+issue_group_assignment:
+  default: 0
 notified_events:
   serialized: true
   default: