TST : added test of creating empty DM
TST : added test of creating empty DM

NSLS-II/dataportal,tacaswell/dataportal,ericdill/databroker,ericdill/databroker,tacaswell/dataportal,ericdill/datamuxer,danielballan/dataportal,danielballan/datamuxer,danielballan/datamuxer,ericdill/datamuxer,NSLS-II/datamuxer,NSLS-II/dataportal,danielballan/dataportal