Added a nbt_node to chunk function and a slightly more user friendly for each chunk function

Signed-off-by: Toon Schoenmakers <nighteyes1993@gmail.com>
Extracting the x and z position of the chunk from raw nbt data

Signed-off-by: Toon Schoenmakers <nighteyes1993@gmail.com>
Added a fairly simple but nasty test case for the for_each_chunk function

Signed-off-by: Toon Schoenmakers <nighteyes1993@gmail.com>