Bug 3206: OAI repository deleted records support.

Bug 3206: OAI repository deleted records support.

This patch allows Koha OAI repository to support deleted records.

The OAI-PMH:DeletedRecord syspref is introduced and can be set to:

- persistent (in case Koha's deletedbiblio table will never be emptied
  or truncated)
- transient (in case Koha's deletedbiblio table might be emptied or
  truncated at some point)

Test plan:

- After applying the patch, test that:
   - Deleted records appear in ListRecords and ListIdentifiers requests.
   - Filter parameters (from, until, set and resumptionToken) still work
     and are applied to ListRecords and ListIdentifiers requests.
   - Identify request shows if the repository is considered persistent
     or transient, according to the OAI-PMH:DeletedRecord syspref.
   - Deleted records that used to belong to a set are still displayed in
     those sets and marked as deleted.
   - GetRecord requests work on deleted records, which are marked as deleted.

Requests examples:
/cgi-bin/koha/oai.pl?verb=ListRecords&metadataPrefix=oai_dc
/cgi-bin/koha/oai.pl?verb=ListRecords&metadataPrefix=oai_dc&from=2015-02-20T11:08:33Z
/cgi-bin/koha/oai.pl?verb=ListRecords&metadataPrefix=oai_dc&set=new_specSet1
/cgi-bin/koha/oai.pl?verb=GetRecord&identifier=KOHA-OAI-TEST:2&metadataPrefix=oai_dc
/cgi-bin/koha/oai.pl?verb=Identify

Signed-off-by: Frederic Demians <f.demians@tamil.fr>
  It works in all situations described in the test plan. Great addition.
  Thanks.

Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>