Minor vehicle class refactoring.
Minor syntax change
Refactroing and debug messages
Fixed issue with music stopping when selectin vehicles.
Game now starts in fullscreen on all platforms.

The game resolution 640x480 is quite old and it does not look good on
hires displays. Therefore, it makes sense that the game always starts in
a window. It can still be run in fullscreen by specifying the
'fullscreen' command line parameter.
Updated documentation and game info.