Moved draw logic from Monster to Creature in a way that will work for Nonplayers as well.
Huge damage/armor rework

* creatures now handle incoming attacks in deal_damage and take damage in apply_damage
* damage can be of multiple types, all of which can be handled differently, separately
* Creature::hit is now a shim for deal_damage, use deal_damage in all future
interactions
* added game::creature_at which is functionally identical to mon_at but returns a creature