Added imageManager to Runtime ( TODO : Images not properly loaded at startup ).
Added support for scaling Sprite objects.
TODO : Polygon collision testing is too expensive. Add a check for basic bounding box and avoid recreating temporaries when returning hit boxes.
TODO : Avoid creating forces each frame.
TODO : Recycle objects.
git-svn-id: svn://localhost@997 8062f311-0dae-4547-b526-b8ab9ac864a5