Make size optional for objectstore file-like objects, better duck-typing the standard library file-like object.
Make size optional for objectstore file-like objects, better duck-typing the standard library file-like object.

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