Mob status

[LogicParrot]

That PR should be finished soon.

Note that squids require a change to the Pathfinder. I'm planning to make the pathfinder more configurable to allow ladder climbing, underwater pathfinding, etc.

Also, we'd need to tune the physics a bit before doing proper jumping for spiders and slimes.

So, my general plan is:
- Mob refactor
- Implement some mobs
- Fix physics (Including player knockback, mobs walking through open doors, etc)
- Update pathfinder
- Implement remaining mobs