Feature mapbox integration 

This adds support for maps rendered using the mapbox OSM android sdk. 

Additionally, the OSM map implementation using the osmdroid library was removed since the mapbox sdk, and osmdroid both use OSM data, and satisfy the same need, and given that the mapbox sdk has more traction.

For the moment, only the `normal` or `roadmap` map view is supported.
Additionally map rotation is not yet supported.