Added prefab delta support. A prefab delta can be included in a module under deltas\(ModuleName)\prefabs\(prefabName).prefab. These may add/remove and alter the fields components, as well as change the prefabs parent.  Deltas are applied in module dependency order, so if two modules apply changes to the same prefab, they module that depends on the other's delta is applied last. If modules without dependencies change the same prefab then the order is arbitrary.
Deprecated the BeforeEntityCreated event.