Infer gene extent only if necessary.
Infer gene extent only if necessary.

Inferring the gene extent is very slow, so check to see if
'gene' and 'transcript' already exist in the file before making
the database.

lpantano/bcbio-nextgen,elkingtonmcb/bcbio-nextgen,mjafin/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,chapmanb/bcbio-nextgen,fw1121/bcbio-nextgen,vladsaveliev/bcbio-nextgen,gifford-lab/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,a113n/bcbio-nextgen,lbeltrame/bcbio-nextgen,chapmanb/bcbio-nextgen,biocyberman/bcbio-nextgen,gifford-lab/bcbio-nextgen,vladsaveliev/bcbio-nextgen,verdurin/bcbio-nextgen,gifford-lab/bcbio-nextgen,biocyberman/bcbio-nextgen,fw1121/bcbio-nextgen,lbeltrame/bcbio-nextgen,elkingtonmcb/bcbio-nextgen,mjafin/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,elkingtonmcb/bcbio-nextgen,verdurin/bcbio-nextgen,lpantano/bcbio-nextgen,brainstorm/bcbio-nextgen,a113n/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,chapmanb/bcbio-nextgen,a113n/bcbio-nextgen,hjanime/bcbio-nextgen,verdurin/bcbio-nextgen,brainstorm/bcbio-nextgen,lbeltrame/bcbio-nextgen,mjafin/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,hjanime/bcbio-nextgen,hjanime/bcbio-nextgen,guillermo-carrasco/bcbio-nextgen,biocyberman/bcbio-nextgen,brainstorm/bcbio-nextgen,lpantano/bcbio-nextgen,fw1121/bcbio-nextgen,vladsaveliev/bcbio-nextgen