Native functions for DLR and ICF

[DaydreamingElephant]

Greetings! DLR (distal -to-local ratio) and ICF (interchromosomal fraction) are parameters used to characterize chromatin compaction in regions of Hi-C maps. They are supported by other research software. I think that cooltools can benefit from built-in functions that will return binned tracks of these parameters.

[Phlya]

ICF is basically part of cooltools coverage, since it calculate both cis and total coverage.
DLR is not directly implemented, but there is this in the sandbox, which will let you calculate it easily: https://github.com/open2c/cooltools/blob/master/cooltools/sandbox/cross_score.py