LP1584891: Export MARC holdings with UTF8 subfields

LP1584891: Export MARC holdings with UTF8 subfields

The --items option of marc_export adds a new MARC 852 field with a
number of subfields that it retrieves from the database. If those
subfields (such as call number, copy location, etc) contain Unicode
characters, then we need to decode the incoming UTF8 characters
when adding the subfield values to avoid corrupting the MARC.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
Signed-off-by: Chris Sharp <csharp@georgialibraries.org>