Lighting finished & new stuff:

- Skylight. Every air block that can see the sky is fully lit.
- Lighting finished. It still needs optimitzation though (like everything
  else)
- New blocks: Cobble, sand, logs, planks.
- Map loading: Now loads dirbaio files.
- Next: Map saving, new thread for lighting updates, re-do frustrum culling,
        make hitbox for player, fix player movement (gravity).