Removed BG2 interfaces

Current API does not handle right-click functionality well, so there is
no point to placing these in the BG2 slots
Fixed Bow, Hammer for BG2

- Removed unneeded interfaces
- Correctly implemented BG2 IAllowItem
- Added ISpecialBow for Hero's Bow, but still need DefaultArrowFire to
be public before all of my 'hacks' can be removed