[Changed] how building objects track child creatures
[Changed] LuaBuildingObject to inherit from TangibleObject instead of
SceneObject
[Added] CreateChildCreature method to LuaBuildingObject

Change-Id: I3e64c9997262404ac32121d4a79a2af219c523bf
Merge "[Changed] how building objects track child creatures [Changed] LuaBuildingObject to inherit from TangibleObject instead of SceneObject [Added] CreateChildCreature method to LuaBuildingObject" into unstable