First biomes!

I am happy to share on this Thursday night that I managed not only to split mesh generation into submeshes to handle different materials, but also reworked interaction with cells. Soon I will post a new version in which you will be able to add and remove cells with mouse click.

Distribution of cell types is implemented with several noise maps, such as height, moisture, and temperature.

Nest steps: optimization and clean-up. Then second itch build :)