update_oai-pmh record adminEmail address

Motivation:

OAI-PMH provides admin contact details as email addresses. This could
prove useful information.  One such situation is when the OAI-PMH
endpoint is not working.  When this happens, the admin contact details
are no longer available from the endpoint, so caching the values would
prove useful.

Modification:

Update code to capture the admin contact information and record it
against the facility-specific information.

If, when updating the OAI-PMH details, the admin contact details are
discovered (from the OAI-PMH endpoint) then any existing contact details
are replaced with the discovered information; otherwise, any existing
admin contact details are left unmodified.

Result:

We collect and cache OAI-PMH admin contact details in the facility
metadata.