BUCX filtering

BUCX filtering

The different menustyle settings have been offering different degrees
of support for BUCX filtering:
  Full       : multi-drop, container-in, container-out
  Trad, Combo: multi-drop
  Partial    : none (to be expected; it explicitly jumps past class
    filtering, where BUCX gets handled, to a menu of all objects)

This adds pickup, container-in, container-out, multi-unwear/unwield,
and object-ID for Trad and Combo, and multi-unwear/unwield for Full.
(Full behaves like Partial for pickup--not sure why--and for object-ID,
bypassing filters to go straight to a menu of all applicable items.)

There are probably several new bugs--this stuff is very convoluted....