Item code cleanup.

Created by: ComicIronic

Made stuff more OOP, less terrible. Runtime operands are shit and if you use them you are shit. Made some procs mob-generic. There are now two procs: get_all_slots(), and get_equipped_items(), which is get_all_slots but without what's in the user's hand. This is different for silicons.

Fun things found in this excursion: aliums have a snowflake copypaste for being run over by a mulebot.