Use Google Play services to retrieve current location

**Not to be merged**

Those three commits install into the source tree, initialize, and then use the Google Play services for getting location updates. I am looking for testers and for feedback here:

- Is there a best way to include the Google Play services to the build without adding them to the source tree?
- Is there a better name than "fused" for the fused provider, as this technical name may confuse users?

Right now, a high accuracy is requested, with updates falling in the 1s-2s interval.

If Google Play services are not available, the former provider (naive network and GPS fusion) will be used instead.