Merge pull request #2991 from raphendyr/username_change_disablation

Add option to disable username changing

diff --cc app/models/user.rb
index b39ee48,7c3a876..a42671e
--- 1/app/models/user.rb
--- 2/app/models/user.rb
+++ b/app/models/user.rb
@@@ -234,8 -234,12 +234,12 @@@ class User < ActiveRecord::Bas
      keys.count == 0
    end
  
+   def can_change_username?
+     Gitlab.config.gitlab.username_changing_enabled
+   end
+ 
    def can_create_project?
 -    projects_limit > personal_projects.count
 +    projects_limit > owned_projects.count
    end
  
    def can_create_group?