(bug 6711) Add and to allow finer control over usergroup assignment. Completely...

(bug 6711) Add  and  to allow finer control over usergroup assignment.  Completely reverse-compatible with existing userrights-based setups, but can replace Makesysop and Makebot and open the door to lots of other things as well.  Could be moved to extension, I guess, but it just seems a lot simpler to have one interface for all adding/removing of groups.