Support bulk editing in new Doc Editor to modify multiple documents at once

Perry requested (in MB-23805) that the new Document Editor be able to support modifying multiple documents the same way in one step.

This will probably require:

1) a multi-editing mode, perhaps with check-boxes to allow selection of the relevant documents to change.

2) we need to decide on the semantics. Perhaps a chance to any row will change all the rows at once?