facing demo

Signed in as __USERNAME__. Fork of the isometric demo with facing decoupled from movement. Gamepad right stick sets the facing direction (persisting when released; arrow keys are the keyboard equivalent); left stick or QWE/A D/ZSC move. Movement never changes the facing. The walk animation always plays the facing direction's cycle: moving backwards relative to the facing runs it in reverse (FWD/REV shown top-left), forward and sideways play it forward for now. Numpad +/− steps the requested speed.