Polish custom world generator

[Smjert]

Currently the worlds are a bit chaotic because the values need to be tweaked.

1. Play with values to obtain a nice terrain for every biome (maybe generate a world with only one biome to see this).
   1a) We need more "real" mountains and caves on the world surface.
2. Sand must be only near water or in deserts. Sandstone or stone should be under it.
3. Lower rivers presence and height (they creates cracks in the surface that seems caused by an earthquake).
4. Snow is flowing in the air sometimes (also caused by rivers code that changes blocks into air).
5. Expand/adjust flora generation: grass, flowers, need more types/shapes of trees, sugar, add mushrooms in the underground caves.
6. Check caves quantity, shape.. play with them, add lava underground.
7. Generate resources: the entry point already exists in the code, we need a formula based on height/layers to put various ores.
8. Add mob spawners randomly in the underground.
9. Randomly add dirt and gravel underground.
10. Add new biomes?

Base code is taken from: https://github.com/begla/Blockmania/, remember to maintain the license in files.