Bug 9760: Simplify local use preferences

Bug 9760: Simplify local use preferences

Removes a lot of code that was needed to handle prefs the old way.

Test plan:
Goto Local use preferences. Do you see some local preferences?
Add a new pref, edit and delete it.
Modify the url to systempreferences.pl?tab=OPAC or tab=log. You should only see
a short message.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Amended patch: Remove the $sth->finish statements
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>