MNT: changes to retrieval functions in core_v0
MNT: changes to retrieval functions in core_v0

 - raise expected exceptions
 - be a bit more robust to input (deal with oids correctly)

NSLS-II/metadatastore,hhslepicka/metadatastore,ericdill/databroker,arkilic/metadatastore,ericdill/databroker,tacaswell/metadataStore,tacaswell/metadataStore,NSLS-II/metadatastore,hhslepicka/metadatastore,arkilic/metadatastore