Keen Modding Live - Player page cleanup

I've continued to tweak the design of Keen Modding Live's player page. I realized that it's not really ever useful to keep the mouse pointer around in fullscreen, so the checkbox that controls that has been removed. The difficulty and keybinding controls have been moved up next to the DOSBox widget. (I had to struggle a bit with CSS to keep the DOSBox centered and get all the controls floating where they should be.) I also made the entire game-and-controls section hidden until all downloading and initialization is finished - that way, the user won't see weird half-loaded elements jumping around.