vehicles.json overhaul and new obstacle parts (Ready for review)

Typed up by Mechanoid on the forums, here is an overhaul of vehicles.json, fixing in a massive amount of (literal) holes in Cata's fleet of vehicles.  Also, I replaced the last of the underbody wide wheels with the correct normal wheels, as they were no longer needed.

Original forum thread:
http://smf.cataclysmdda.com/index.php?topic=3739.0

EDIT - This has grown from a small patch job to a thorough rebuild of nearly every vehicle with an interior in Cataclysm.  Tested and everything works fine, so this is ready for review.