Graphics update

Not a visual update so much as a handling update from a programmer's perspective. I've been reorganizing the bitmaps to use masks for the faction coloring instead of individually saved faction-specific unit graphics. This will save a small amount of disk space, but more importantly standardize the way images are rendered and reduce the code needed to iterate through drawing the units. It's something that's much easier to do now that I've switched to a new universal-platform language.