Improve Book Author Import GH2780/2803
(1) Set up author bios to get exported/imported the same way that we do the book long descriptions, to avoid the need to truncate them.
(2) In the Acumen-Plone sync, automatically check the "Show in byline" box for all contacts if there are three or fewer authors on the book's roster. Note that we'll manually update book rosters for this when there are four or more on the book's roster.
Completed Jun 2019.