Use dumps of the GeoNames database to resolve geographic region names

Created by: adamreichold

For now, I am envisioning a manual process of indexing the GeoName database dump via

> cargo xtask geonames < path/to/allCountries.txt

and then copying data/geonames to the server. In the long run, this is probably a good candidate for a manually triggered but automatically executed CI job.

Closes #78 (closed)