Re-implement Polymorphing.

This system is quite different from the default Bioware version.  It does not unequip items unless absolutely necessary.
An additional column in polymorph.2da controls which items are unequiped.   The default value only unequips, righthand,
creature attacks (but not hide), and ammo by default.  Lefthan, if a weapon, is always unequipped.

Some other changes:
* Allowing the items to merge into the shape, required modifying when monk abilities are available.  Viz. whenever polymorphed.
* It also required changing AC calculations to always use full dexterity when polymorphed
* Since physical AC bonuses are not merged, those have become only applicable when not polymorphed.
Merge branch 'feature/polymorph'