Added new skills RandomPack and NewTarget and bug fixes

Added new skills RandomPack and NewTarget, fixed bug with spawning snowmen bosses, and fixed bug where swarm skill was spawning 1 more mob than intended.

RandomPack uses a random pack skill from the list that is not on
cooldown:
- randompack pack1,pack2,pack3 >0 1

NewTarget will make the boss choose a new target to attack and for
skills (this includes delayed skills that are already in progress).
- newtarget radius >0 1