Fix bug with player's position not saved sometimes

If the player is flying, or falling or deep underwater, his position
was not being saved.
Change veh saving logic a bit

Make it so that purchased, and mission vehicles are saved regardless
if the player has gotten into it or not.
Minor fix in vehicle position saving

Had wrong variable name
duh, forgot to actually set the position
Improve vehicle saving logic

Make the vehicle saving logic more closely match the vanilla logic
Also, add an option for enabling disabling saving of town vehicles
Player does not need to get into purchased vehicles at least once
for them to be saved.