Bug 14639: Extend Koha::MetadataRecord to handle serialization format and record id

Bug 14639: Extend Koha::MetadataRecord to handle serialization format and record id

The description of this changes is on the regression tests commit
message.

To test:
- Apply the test patch
- Run
  $ prove t/Koha_MetadataRecord.t
=> FAIL: Tests fail because changes are not implemented
- Apply this patch
- Run
  $ prove t/Koha_MetadataRecord.t
=> SUCCESS: tests pass
- Run
  $ prove t/Koha_Util_MARC.t
=> SUCCESS: it still passes
- Sign off :-D

NOTE: Tested as above. Read code. Seems to cover all cases.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>