Debug commit
Added code to replace sprites with a checkerboard pattern in order
to identify filtering issues.
This version only renders DrawSprite()'s with the checkerboard pattern
for debugging purposes
cleaned up some unneeded stuff
306cedbeb213
fixed several 'retina display' images and added a bunch more (though just from upscaling the normal ones; might be nice to have 'em redrawn at a real higher resolution)
