Displays fill levels and prices in tonnes instead of liters.

Affects:
- the fill level display (HUD box on vehicles, trailers and silos)
- the Prices menu (storage amount and sell/buy prices)
- the Animals menu (food and condition)

Liquids such as water, slurry, milk or diesel are still shown in liters.

The game settings let you choose whether prices are shown per tonne (1 t = 1000 kg) or per 0.1 t (100 kg).