Add SOMATIC flag for FreeBayes records

Initial step to address issue #317, but it is not hooked yet to the pipeline
Merge branch 'master' into vcf-somatic-fix
Hook the somatic fixing to Freebayes's paired pipeline and make the move
be in place
Merge remote-tracking branch 'upstream/master' into vcf-somatic-fix
Handle correctly the result from INFO tag adjustment: PyVCF writes
uncompressed, so we have to compress the result ourselves
Merge pull request #350 from lbeltrame/vcf-somatic-fix

Add SOMATIC flag for FreeBayes records