Lighting broke yesterday because initialization code was moved into the wrong place. Sigh. Now we have working scene lighting again.

Redone sprite node classes to inherit from our own base ITSpriteNode instead of SKSpriteNode, so common IsoTile logic can be added there. For now there are north/south/west/east relations to neighboring tiles on the map, and objects placed on the map can simply ask their parent tile for directions when then want to move around.

I’ll probably need to refactor some generic ActorSpriteNode code out of PlayerSpriteNode when the need to add AI actors to the scene arises.