dbNSFP: update to 2.8
Remove 'seleno' tags from the GTF file before using it.

These are bugged and get represented as duplicated transcripts;
it only affects GTF files with the gencode annotations, and it
is only 25 genes.
Narrow fix to Selenocysteine containing lines.

This preserves 25 genes that would have been filtered out in
hg19.
Support automated installation of isaac aligner and variant caller from bottles to avoid large compile steps