fixtures: add OaiHARVEST sources

* Adds arXiv OAI Harvest source used to run
  harvesting workflows.

* Updates the IDs used for OAI related fixtures.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Merge pull request #4 from jalavik/oaiharvest-config

fixtures: add OaiHARVEST sources