3D Part Preview added to Parts Tracker

[Philippe Hurbain]

To follow up on a couple of feature requests from the internal pre-launch thread:
- BFC Colors
- Random quad/tri colors

Both of these features are possible with Lasse's renderer and will be added at some point in the near future.

Another addition that would be useful (no idea of complexity involved!): possibility to display an origin/axis thingy to allow quick check of part origin and orientation...