sec: use jquery ui tabs for machines in security preferences

sec: use jquery ui tabs for machines in security preferences

This will degrade gracefully and operate without javascript. The
previous interface of having to switch by submitting a form was
unpleasant.

Note that it makes little sense to have cron permissions on webservers
you can't login to, and we're down to just firewall and cron prefs
here. The page should probably be converted to just firewall rules,
and cron prefs handled in a separate support page (and both new pages
moved to Support).