remove XUL @persist from list column definitions

We moved away from @persist a long time ago, but some cruft remained.  This
would cause a local file, localstore.rdf, to balloon in size as columns were
adjusted in XUL-based lists.  Since this is an XML file, writing and parsing
it can get very expensive if the file grows too large, which it has done for
some people.

This change keeps that file from growing further based on these list columns,
but it may be worth deleting the localstore.rdf file or creating a new staff
client profile (uninstalling and reinstalling the staff client DOES NOT
accomplish this).

Signed-off-by: Jason Etheridge <jason@esilibrary.com>
Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>