Multiple author handling

[thatandromeda]

Multiple authors:

• Can we also check the received field in Elements to decide whether to request from a second author, rather than simply reject it as already requested? (use case: request from author Write Elements app #1, don't receive, a few months later request from Write auth/users app #2) (alternately, would this be better as part of the Elements filter?)
• If you import multiple citations at the same time for one paper with multiple authors, requesting from all authors is fine (for the moment - people need to figure out their workflow)