Bug 16167: Remove Authorised value images prefs

Bug 16167: Remove Authorised value images prefs

There are 2 prefs to drive this feature: StaffAuthorisedValueImages and
AuthorisedValueImages. AuthorisedValueImages is not added by
sysprefs.sql and does not appear in updatedatabase.pl, we could easily
imagine that nobody uses it.

With XSLT enabled, the feature is only visible on a record detail page
at the OPAC, if AuthorisedValueImages is set. Otherwise you need to turn
the XSLT off. In this case you will see the images on the result list
(OPAC+Staff interfaces) and OPAC detail page, but not the Staff detail
page.

This patch suggests to remove completely this feature as it does not
work correctly.

The ability to assign an image to an authorised value is now always
displayed, but the image will only be displayed on the advanced search
if defined.

Test plan:
Confirm that the authorised value images are no longer visible at the
opac and the staff interfaces.
The prefs should have been removed too.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>