Versatile 500 - Fix v1.2.1.0

!Release!
Who's ready for another Versatile! I've been working on this one for a bit as a way to learn how the XML works. All of the errors have been cleared aside from some missing audio files that I should have fixed in the next update.

So What's fixed!?
Cleared up the previous LUA errors.
Fixed the wheels, now all wheels are powered not just the front two.
Corrected the mass and torque so that it doesn't run like a race car and flip over all the time. Still a WIP as it seems just a touch under powered pulling up hill.
Added flex to the center pivot joint so it doesn't act like a rigid frame any more.

All credit to all of the previous people that worked on / created this mod. There's so many versions out there with different credits it's hard to know who to attach it to. This is just my edit fixing the things that bothered me. More to come as I figure out the XML.