Add call to EntityLiving when counting entities for Spawning Cap

Potential Use Cases:
* Create 'animals' / 'ambient' creatures without being forced to follow the vanilla class hierarchy (i.e. extend EntityAnimal or EntityAmbientCreature)
* Have Hostile creatures that can be 'tamed' and no longer count towards hostile spawn cap
* Extends vanilla creature hierarchy but not count towards spawn cap for default monster/animal/ambient cap