* Do cleanup onGroupUse and onGroupAdd

Cleanup scans for forms that the player no longer has favorited, or
optionally no longer has (getitemcount == 0).
* Auto-clean nearly full groups in onMenuClose

Groups are flagged for a check if an added item pushes their count over
28/32.  This should prevent the UI-lagging CleanupGroup function from
being needed in all but the most extreme cases (i.e. the user is
intentionally trying to break the group system by adding tons of items).