ILL: redesign Config object, new Record object.

* Koha/ILL.pm (new): add config Object.
  (config): return 'config' Object.
  (search): use Record objects to return array of objects.
* Koha/ILL/Config.pm: significant re-write to fulfill new role.
* Koha/ILL/Record.pm: new file defining the ILL Record object.
* etc/ill/config.yaml: restructure to match new role.
* ill/ill-requests.pl: remove deprecated Config references.
* ill/illrequest-new.pl: remove deprecated Config references.
* members/illrequests.pl: remove deprecated Config references, add
  temporary illustrative testing code.
* opac/opac-ill-request.pl: remove deprecated Config references.