Bug 9755 QA follow-up: move MARC-specific functionality to utility class

Bug 9755 QA follow-up: move MARC-specific functionality to utility class

This follow-up moves all the MARC-specific functionality of Koha::Record
(now renamed to Koha::MetadataRecord) to a Koha::Util::MARC utility class.

To test, run relevant unit tests:
> prove t/Koha_MetadataRecord.t t/Koha_Util_MARC.t t/db_dependent/Koha_Authority.t
and optionally try to merge a record.

Signed-off-by: Mathieu Saby <mathieu.saby@univ-rennes2.fr>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>