Editors sometimes need to create anonymous articles

[joemull]

Problem

Journals often need to publish anonymous content on Janeway--things like forewords, editorials, and front and back matter from legacy formats.

However, due to the need to have a correspondence author and article owner during production, Janeway prevents editors from deleting an author record if it is the last one.

Proposed solution

Let editors delete the last author record, with warnings:

1. normal production cannot proceed without a correspondence author, so the article should be in a ready-to-publish state or the editor should plan to move it through the workflow in another way
2. the editor / current user will be made the "owner" of the article