LP#1086458: clean up after event listeners in circ/patron interface

LP#1086458: clean up after event listeners in circ/patron interface

Upon window unload, now removes event listeners, both ones explicitly
created by the page JavsScript as well as ones created by
util.list, util.controller, and persist_helper().

The same approach of defining cleanup fnctions used by unload
events can be applied to the rest of the staff client, but
this patch focuses on circulation first.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Ben Shum <bshum@biblio.org>