Investigate VCF files from ICGC

[agduncan94]

Investigate whether the BAM files from ICGC work with the variant track.

Note that first party ICGC data should include index files. For this data, you should be able to point the variant track at the BAM and index file (with modification for adding the token).

The ICGC API returns the index file information (https://dcc.icgc.org/api/v1/repository/files/FI819885) so we can use this to create the track.