Remove biomes

[0xhank]

Biomes are bad for a few reasons:

1. They make Dark Forest confusing to new players. Even I still don't fully understand what they do for all game entities -- this is because they impact planets and artifacts in very minor ways that aren't really meaningful.
2. They don't add depth to advanced gameplay. I'm okay with a feature compromising legibility if it creates dynamic, deep gameplay, but biomes just don't.
3. They bloat the codebase. I'd rather use Smart Contract and client space to have exciting stuff instead of biomes.