Fixed Camera, layer transition, background assets

Camera zoom in zoom out fixed. Parallaxing now works by using multiple
cameras. Added assets for background layer. Background layer comes
forward, but it still has the assets for the background objects and the
objects brought forward do not match objects "seen" since the objects
that are seen aren't actually at that location--they are projected
behind the player character and into view by the secondary camera.
i.e.: background object is actually at (2, 20), but player character is
at (10, 15), the secondary camera projects the view at (2, 20) behind
player; when bg objects are brought forward, the main camera will
project the objects at (10,15). Also, there will always be some sort of
null error after transitioning and no new objects in the background are
created.