Start of swipe gesture handlers
Added a Game manager singleton. Added swipe to pref and next race.
Created a third race track
Swipe through three race scenes
Changed the sprite size for iPhone retina to be the same as iPad and renamed with @2x suffix to prevent being automatically doubled. This makes the images full resolution instead of zoomed half size images. they look much better.
Reduced the car size by half - quarter area.
Added a second truck with common throttle. Other controls affect user truck only.