The ":" character will be reserved for default permissions, so that
users cannot create a permission with a name that will later be
added as a default.
Allow the ":" character modifying/deleting permissions*, but not
when creating them. Also do not allow the new name to contain ":"
when renaming.
(* modify/delete have unrelated restrictions on managed permissions)
Reviewed-By: Martin Kosek <mkosek@redhat.com>