Moves some spells to a new equipping type

Created by: ComicIronic

Equip-type spells now read from an assoc list of slot ids and types, as well as using OOP procs for item generation. Clowncurse, frenchcurse, and horsemask have been migrated to this system. This is framework that hopefully clockcult and other summon-item spells can use.

Also changed some instances of user to holder, because I'm planning something.