Twohand system rework
Created by: ComicIronic
Added general procs for wielding and unwielding. Added the TWOHANDABLE and MUSTTWOHAND flags. Made code more OOP. Any item can now be twohanded, and twohanding is now done by holding an item in one hand and clicking it with the other. You can switch hands while wielding now, which is only useful in dropping the offhand to stop wielding.