Bug 12252: OAI-PMH result includes item data

Bug 12252: OAI-PMH result includes item data

GetRecord for OAI-PMH was pulling the MARCXML directly from the
database. Now it uses GetMarcBiblio and includes the item data with it,
making it more generally useful.

Test plan:
* Run an OAI-PMH query, for example:
http://koha/cgi-bin/koha/oai.pl?verb=GetRecord&identifier=KOHA-OAI-TEST:52&metadataPrefix=marcxml
  to fetch biblionumber 52
* Note that it doesn't include the 952 data
* Apply the patch
* Do the same thing, but this time see that the 952 data is at the
  bottom of the MARCXML.

Note:
* This patch also includes a small tidy-up in C4::Biblios to group
  things semantically a bit better, so I don't spend ages looking for a
  function that was staring me in the face all along again.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Works as described. Simple yet useful patch.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Frederic Demians <f.demians@tamil.fr>
952/995 item fields are back in response to GetRecord OAI verb.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Signed-off-by: Gaetan Boisson <gaetan.boisson@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>