comma separated list of fields that get substituted into templates in
places of the E<lt>E<lt>items.contentE<gt>E<gt> placeholder. This
-defaults to due date,title,author,barcode
+defaults to date_due,title,author,barcode
Other possible values come from fields in the biblios, items and
issues tables.
=item E<lt>E<lt>items.contentE<gt>E<gt>
one line for each item, each line containing a tab separated list of
-title, author, barcode, issuedate
+date due, title, author, barcode
=item E<lt>E<lt>borrowers.*E<gt>E<gt>