Major Sfc_Game.py update

Sfc_Game.py updated to use the concept of "dirty rectangles" to redraw
only what has changed, rather than redraw the entire screen each time as
before. Note that for now there is effectively no difference from
before, as the program is still the panable background, and thus the
entire screen is redrawn anyway. BUT the approach will make further
development much cleaner. Main has been changed accordingly to work with
the new style.
Deleted unneeded file.