MNT: Added optional dictionary to event descriptor
MNT: Added optional dictionary to event descriptor

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