Added Jewel of Froz properties for changing item behavior on the fly. Increased JoF hitroll, reduced mana cost. Fixed item equipping issues in the ITEM_USE_HAND slots.

-Turned many variables in frozjewl.kod into class var/properties so they
can be changed for all JoFs in-game, or modified individually for
testing.
-JoFs now offer a flat 200 hitroll bonus each, scaled by % of max
attainable HP (up from 30-150). Scaling can be turned off, but is on by
default. Bonus value can also be modified.
- JoFs now only cost 1 mana each to use, even if two are present (down
from 2 mana each if two are present). Double mana usage can also be
turned back on if necessary, and mana lost per jewel can be modified.
- Fixed all the wielding issues where players can wield 3 or more items
(e.g. weapon/JoF/shield, JoF/JoF/torch, etc). All should now work
correctly, however double JoFs will still not work with a soldier
shield.