[CR] Diesel engines.

- V6, V8, and straight-6 diesel engines.
- Diesel fuel from pumps at gas stations
    ( One in six chance of replacing a normal gas pump with diesel. )
- Diesel fuel tanks in three flavors: normal, small, and external.
- Ability to siphon both gasoline or diesel fuels.
    ( Both through the vehicle GUI and by activating the rubber hose item )