Item use/equip/drop/junk

[ethanmoffat]

Implement UI bindings for item actions. Depends on #138 being done.

Double-click from inventory:

• Use - should invoke the correct action based on the item type
• Equip - should equip the item and make it visible in player's paperdoll

Drag to map: should drop item and prompt if there's more than 1 for how many to drop
Drag to drop: should drop item below character / prompt if there's more than 1

Drag to junk: should junk item after confirmation dialog / prompt if there's more than 1

Paperdoll button in inventory should also be hooked up