This fixes all cases where the color profile was broken, and
libpng warns about. It also makes almost all textures indexed
instead of RGB where possible (textures that don't have
semi-transparent pixels).
- API {farming.register_hoe(), farming.register_plant()}
- Fertilities -> Plant only grow on soil with a fitting fertility, e.g. Wheat only grows on grassland, while cotton grows in deserts and grassland)
- New soil: Desert Sand
- Place seeds instead of plants
