Bug 22311: Add a SysPref to allow adding content to the #moresearches div in the...

Bug 22311: Add a SysPref to allow adding content to the #moresearches div in the opac

The idea of this development would be to match the syspref 'OPACSearchForTitleIn' but
for populating the search headers (#moresearches) on the opac page to allow staff to
easily add links without jQuery.

Test Plan:
1) Apply this patch
2) Run updatedatabase.pl
3) Update the new OpacMoreSearches system preference to include the following line:
    <li><a href="https://duckduckgo.com/">Duck Duck Go</a></li>
4) Browse to the OPAC
5) Note your new link displays in the "moresearches" area of the OPAC.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>