Add PathfinderGoalSit for diff visibility
Fix "setSitting" on tameable animals. Fixes BUKKIT-1534

This makes it so animals (tame or not) will sit properly and not move
around.

Wild animals that are sitting may override the sitting position if
they are attacking.
Move the tile entity with the falling block. Adds BUKKIT-3349

Allows for interesting things to be done with world.spawn()
Implement fishing experience. Adds BUKKIT-3348