base: test records loading

* Enables inveniomanage demosite populate with custom xml.
    
* NOTE: Before populating DB with demo records from custom xml
  please make sure that BASE_DEMOSITE_RECORDS_FIXTURE
  is set to list containing proper filenames


Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>
Well this part precisely I think it will be same, the change will be in the actual call the bibupload/uploader