Salvage in butcher menu, inv filter, autosalvage

Behold: a major game enhancer PR. At least for people who want to keep their game areas tidy.

Adds salvage function to butcher menu (like disassembly). This currently uses tool quality "CUT" rather than checking for actual knife function (and using the item), but cutting tools are cutting tools.
Salvage entries in menu have "Cut up " prepended to show that it's not just disassembly, but possibly wasteful salvage.

Next it adds autosalvage: an extended action that salvages all salvageable items on the tile. It uses the regular salvage function so it is not interruptible during individual item cutting, only between items.

Cut menu (from knife function) now filters by salvageability.
Fun fact: thread is salvageable into rags.

Also fixed a tiny bug where not having a butcher item would prevent disassembly from butcher menu.