Bam_Stats nodes now require date; fixed a test that broke due to perltidy
an instance of Schema now stores a unique instance of Graph on itself
graph/schema node adding methods now take enqueue option with queues the adds until new dispatch_queued() method is called; various methods optimised for speed by conversion to subs; vcf_genotype_comparison step uses enqueue for massive speed-up
Merge branch 'develop' of /software/vertres/git/origin/vr-pipe into develop