Trust WiFi positions over GeoIP results, closes #296.

Also remove two tests for impossible conditions: A mismatch between
a cell position and its mcc. We do filter these out on ingress.
Update to latest version of country-bounding-boxes.

Welcome Gibraltar and Tuvala :)
Merge pull request #298 from hannosch/296-trust-wifi-over-geoip

Trust WiFi positions over GeoIP results, closes #296.
tag
Add a header row to the exported CSV files, refs #282.

I've been unclear on this one, sorry @graydon!
Initial sketch of OpenCellID import code, cc #283
Support and test OCID cells in ichnaea.service.locate code path, cc #283.