Outdated D-Troxx Truck, Trailer and Bus Wheels 1.3.2

Fixed "Flat wheel" model not appearing as reported by @Bolt2407_Beamfan

Thanks to @Gregory TheGamer for fixing my stupid material mistake.

Made a few fixes and added the new PBR textures.

PBR stuff still needs some adjusting but will do that later when I have time.

Small update for extra wheel options with the upcoming Gavril T-Series Expansion Pack update

This update brings the following:
- 3rd axle support for gtg truck mod
- Flat steel wheels

Added 5-Slot version of the steelies.


Also added the wheels to the trailer bogie's and the bus.