Support for Mozilla Location Service (A-GPS)

Currently, A-GPS is only available on commercial UT-devices through Nokia HERE. This is a real problem for users of community ports (like those provided by ubports.com). Also, the HERE service is closed source and proprietary, that's kind of odd for the free operating system we all want Ubuntu Touch to be.

I suggest that we try to implement the Mozilla Location Service, which is a free and open source location service: https://location.services.mozilla.com/

There is a bounty on Bountysource on this: https://www.bountysource.com/issues/39808752-support-for-mozilla-location-service-a-gps