See issue #590
This switches to using the Wikimedia tile server for providing map data. It comes with a couple of drawbacks which are currently unavoidable, but such is the way of open-source...
- The WMF map server does not provide vector tiles, or rather it doesn't provide vectors that are compatible with the Mapbox SDK :(
- It provides only one "theme" of tiles, so you will no longer have a dark vs. light theme.
