Presence Footsteps

Changelog:

- All the fixes included in r24-1.15.2
- Added the "locomotionmap"! All mobs (with precious few exceptions: fish, flying entities, birds) will look at this map to determine whether to produce footsteps and if so, how many (biped/quadruped)

Todo in the next version:

- Add better integration for Mine Little Pony so ponified mobs can produce quadrupedal footsteps
- Update to a newer snapshot
- Learn not to procrastinate