Derby and Stock Car Skin Pack for the Moonhawk 1.3

This release incorporates two new official parts, the roll cage and the doors without door panels. Also made improvements to the skins by painting over the chrome trim and bumpers. Added a bump map to the interior skin. Split the skins into two configurations, the plain cars with numbers only are configured for demo derbies while the cars with sponsors are now hopped up for the track. This release does drop the dirt-covered variations for the time being as I could not get them to look right where the trim and bumpers have been painted over.