Add migration script for coverage scores.
Add migration script for coverage scores.

thomaskonrad/osm-austria-building-coverage,thomaskonrad/osm_austria_building_coverage,thomaskonrad/osm-austria-building-coverage,thomaskonrad/osm-austria-building-coverage,thomaskonrad/osm_austria_building_coverage,thomaskonrad/osm_austria_building_coverage,thomaskonrad/osm-austria-building-coverage,thomaskonrad/osm_austria_building_coverage