add incidence rates (and specific cell lines) of variants in CCLE data

[andrewsu]

[newgene]

@andrewsu can you please locate the particular data file at https://portals.broadinstitute.org/ccle/data?

[andrewsu]

ugh, CCLE terms of use are pretty restrictive for redistribution https://portals.broadinstitute.org/ccle/about. Useful data and they do provide it in a structured format that could be easily parsed, but we'd have to reach out to them first on getting permission (like exac and gnomad)...