Add versioning information about the maxmind database being used
In https://lists.torproject.org/pipermail/ooni-dev/2014-July/000125.html Choke point project expressed the need for having the version number of the maxmind database being used.
This could be a timestamp of when the database was retrieved and a shasum of the file. The versioning information should be part of the ooni-probe report in the header.