Full FAR compatibility (corrent terminal velocity and stock-equivalent drag coefficient)

Hi, as I wrote in a PM a few month ago, I've implemented full FAR compatibility.

Unfortunately I did not do the announced re-write of my impact code (which would have done full terrain intersections).

During testing I've come across a strange Exception during DrawSurface; the stack trace points somewhere into the Unity Graphics drawing methods; I was not able to reproduce the issue, and have no idea where it is coming from. I _assume_ that it has nothing to do with my code, but I could of course very well be wrong with that.

I have surrounded the whole DrawSurface method with a try/catch blog in the hopes of catching more stack traces, but so far I've not managed to.

This is the Exception text from the debug menu:

IndexOutOfRangeException: Array index is out of range.
ArgumentException: Getting control 1's position in a group with only 1 controls when doing Repaint
Aborting