API : restore id on event documents
API : restore id on event documents

Turns out the value of `_id` is leaking out and being used
elsewhere in the stack.  Restore this to un-break the API.

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