Merge pull request #48 from srl147/devel

pb_align: check flagstats before AND after spatial_filter, fix for singl...
Merge remote branch 'srl-local/devel' into devel
Refactor code for adding BAM header PG records (and only add a single record for spatial filter)
Merge pull request #6 from dkj/devel

Refactor PG BAM header record adding