Made diesel render as brown in vehicle ui, fixing all resources
colours after gasoline, including water
Copied definitions of fuel_types and fuel_colors across to
veh_interact.cpp to fix fuel usage indicator colour. Moved them to the
top of both files if they weren't there already.
Redefine fuel_colors in header as extern, so veh_interact can use it.
removed magic number
prevents more than 5 fuel gauges rendering on vehicle ui
Added debug message