Remove locality pointers

- They weren't necessary and the xor did not work with them
Add locality uint16 to chunk/metachunk

- When using parent to traverse neighboors, it is almost necessary
  to know which coord you occupy in the parent's 8x8x8 cube.
Remove premature optimization (again)

- The uint16 was too complex and not much less wastful than 3 uint8s
- Uint8 were left in its place with friendly names.