Bug 7345: Enable exporting records sans private fields

Bug 7345: Enable exporting records sans private fields

Add an option for marcstd to the opac-export.pl and catalogue/export.pl
scripts. This new format removes all 9XX, X9X, XX9 fields and subfield $9
(with the exception of 490 in flavours of MARC other than UNIMARC). The work is
done in C4::Record::marc2marc.

This patch adds the new export option 'marcstd' for exporting MARC
records without 9xx, x9x and xx9 fields and subfields to the staff
detail page.

Testing plan:
1. Export a record in "MARC (Unicode/UTF-8)" format as a control
2. In the OPAC, run the following jQuery to add the marcstd option to the UI:
> $("#export #format").append("<option value='marcstd'>MARC (no 9xx)</option>");
3. Export the same record in "MARC (no 9xx)" format
4. Compare the two, noticing that any subfield $9 or fields including 9 (other
   than 490 in flavours of MARC other than UNIMARC) have been removed

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Works as advertised now.
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
This patch squashes both the original patch and Katrin's follow-up adding
marcstd as an export option on the staff client.

Feb 13, 2012 (marcel): Amended this patch to resolved two definitions of $error in catalogue/export script.