GITC-6411 Created mrf_unjoin script to break up MRF into cells

[jtroberts]

No description provided.

[lucianpls]

What is the application for this?
It should be possible to do without compression/decompression of tiles, just by creating new index files (and optionally copying the needed tiles), making it indeed the reverse of the join.

[jtroberts]

It is to support a GIBS processing workflow that needs to occasionally reprocess cell MRFs that no longer exist. I think we could just use mrf_insert to update the final MRF but that's either difficult or not efficient for the workflow (I don't recall the exact reasons).

I initially looked at creating new index files and copying the tiles but saw that the tile matrix sets did not match. For instance, the MRF has 20x10 tiles but we needed to break into 16x8 MRFs. The approach in the current script has decent performance and is reproducible with gdal commands.