[#572] Redirect to download SatStat APK
[#572] Redirect to download SatStat APK

* Changed URI to /gps
* Using Datastore entities instead of Properties file to store redirect address
[#572] Remove unused import
[#572] Using neutral constant for GPS URI
Merge pull request #573 from akvo/issue/572

[#572] Add URI to download SatStat APK