Scrapped the old actor system
Added new actor system

- a wrapper StaticActor for Sprites and AnimatedActor for Animations
- LayeredActor holds a list of StaticActors/AnimatedActors
- all of the above extend ModelActor, which represents a Model
- should allow the desired level of granulity, while making it possible
to control each sprite/animation individually via events (ships with
scriptable moving bits)