Support for snpAD

[apeltzer]

We should have support for snpAD, additionally incorporating mapability tracks if possible.

[jfy133]

Slight problem, not on conda and not github either :\

https://bioinf.eva.mpg.de/snpAD/. Dunno if they will allow that if (bio)conda can't verify stability of the lnk...

[sc13-bioinf]

I made a nextflow pipeline for snpAD so you can copy some of that if you want. The main reason my pipeline sucks is that it builds the substitution model for all chromosomes. You can just do that for one chromosome (or maybe X.Y.MT also if you really want) and then use that. Its in my HOMErepos/nextflow-snpAD but its not a git repo.