Move responsibility for lac entry deletion into update_lac task.

This simplifies the remove_cell task a bit.
Update radio types for GSM (#304)

- Update cell processing to catch incorrect radio types
- Add test
- Add data migration
Correct missing bits of migration step, add changelog, closes #304.

This moves the `create missing lacs` part at the end of the migration and
corrects the unique cell statistic after the latest migration again.
Move lac update scheduling to Redis based queue (#287)