fix bug in dryad-pages.js around multiple author reordering events

The previous commit of themes/Mirage/lib/js/dryad-pages.js had
a bug in its handling of multiple author re-ordering events, where
event binding was being lost after the first reordering of
author names on the describe-publication page. This commit
re-binds onchange events for author name rows, improves handling
of select/option data, and slightly cleans up code in the
reorderAuthorOrderOptions() function.