DOC/MNT: fetch_events_generator
DOC/MNT: fetch_events_generator

Document and clean up fetch_events_generator

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