CWL: add run_number target for manual CWL update
CWL: add run_number target for manual CWL update

Enables forcing re-run of completed steps if there are problems or code updates
by updating a run CWL.

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