Material Slots

Do allow the game to swap materials at runtime, we need to know what slot is what.

For bodies, there are place holder materials found in /Cars/Bodies/Meshes.

For Fixtures, there are place holder materials found in /Fixtures/FixtureMats/...?

Fixtures also need correct material slot names:
 * panel_1
 * panel_2
 * glass_1
 * opaqueglass_1
 * trim_1
 * grill_1

The numbers are open ended, should start at 1, and go up to as many as required.