Add support for 4 file format to single cell handling.
Add support for 4 file format to single cell handling.

brainstorm/bcbio-nextgen,brainstorm/bcbio-nextgen,biocyberman/bcbio-nextgen,biocyberman/bcbio-nextgen,chapmanb/bcbio-nextgen,lbeltrame/bcbio-nextgen,lbeltrame/bcbio-nextgen,a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,chapmanb/bcbio-nextgen,biocyberman/bcbio-nextgen,brainstorm/bcbio-nextgen,a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,a113n/bcbio-nextgen,chapmanb/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen