Initial sketch of OpenCellID import code, cc #283
Support and test OCID cells in ichnaea.service.locate code path, cc #283.
Address review comments, cc #283.
Add support for importing already-existing rows as updates, close #283.
Address review comments, cc #283.
Remove AUTO_INCREMENT=34 from alembic sql.
Accept float ranges in import, convert to int.
Skip header row on import.
Commit each batch of imported values as they are imported.