UV update and Mesh improvements

I've been working on painting the vehicle but couldn't quite get there due to various technical issues on my side.

While I was trying to get the paint done I made a LOT of mesh improvements, fixed a few things I missed the first time and UV mapped every object by hand (except the tracks because *screw* the tracks)

- improved and fixed errons on the tracks
- Applied transforms correctly (I hope)
- UV mapped almost every object
- improved the trackguard
- added flat planes option for the engine air intake
- fixed face orientation issues
- A bunch of other things I dont remember anymore cuz I worked on this for so long