* Move all collision code into the pkg/collision package. * pkg/doodads/collision.go -> pkg/collision/collide_level.go * pkg/doodads/collide_actors.go for new Actor collide support * Add initial collision detection code between actors in Play Mode.
* All private Doodle source code into the pkg/ folder. * Potentially public code into the lib/ folder. * Centralize the logger into a subpackage.
