base: Test records for Zenodo

* Enables inveniomanage demosite populate with custom xml

* Adds XML with test records for Zenodo.

* NOTE: Before populating DB with demo records from custom xml
  please make sure that BASE_DEMOSITE_RECORDS_FIXTURE
  is set to proper filename (eg. demo_zenodo_record_marc_data.xml)

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>
Not sure about the name - anybody have other suggestions?