title: Add roles field to FOSUserBundle group form
body: <p>When activating group( base on its <a href="https://github.com/FriendsOfSymfony/FOSUserBundle/blob/master/Resources/doc/groups.md" rel="nofollow">documentation</a>) in FOSUserBundle, the group roles are not embedded on edit and update form!I already override GroupFormType and GroupController but I can't pass roles from controller to form class.
  my question is how can I add roles to form to let administrator change or assign role to groups?</p>