Full car coloring with skins

[MirceaKitsune]

I can do the skins for some cars for now. There are many of them in SVN, so there would be a lot of work overall.

The good side is that compatibility is kept with older skins, the way I see this. If we don't update the skins for some cars, the new color chooser would just not work for them, but the current skins would be applied like before. So we can do a few skins now so the new system works somewhere, and slowly convert more of the cars in time, if that would be alright and agreed on.

If so, how many cars would need new skins for a start? And how should I try to make the new skins (like how do I name the new color map, and do I make it a tga with alpha channel or a png with transparency)?