Bug 7392: Add system preference to define export options in OPAC

Bug 7392: Add system preference to define export options in OPAC

NOTE: Patch depends on changes made for bug 7345 for the "marcstd" option.

It adds a new system preference 'OpacExportOptions':

The new system preference allows to give a list of | separated
values to define, which download options are offered in OPAC.
Possible options are listed in the system preference editor
and include the new export option 'marcstd' from bug 7345.

The sequence of the download options in the system preference will
be the sequence in the OPAC pull down.

If left empty, the export option will be hidden from OPAC.

This patch creates a new include file for the OPAC with all the
code that is common to the three detail views (regular, MARC, and
ISBD).

As a side effect of creating this include file, some inconsistencies
in OpacSearchForTitleIn were fixed. {BIBLIONUMBER} and {CONTROLNUMBER}
were broken for ISBD and MARC view before and should now be replaced
with the correct values in all tabs.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Resolved merge conflicts on sysprefs.sql and updatedatabase.pl.

Feb 13, 2012: Rebased it again.