Added TeleportNear ability, and changes bosses to dig out instead of suffocating when underground

Added TeleportNear ability, teleports the boss to a random spot within a certain distance of the player instead of on top of them.
- teleportnear horizontal_radius:vertical_radius >0 1

Also changed it so bosses that spawn underground will dig their way out to the surface instead of suffocating to death or becoming stuck in terrain.