Issue #26: Add setting to choose between high accuracy or power saving, for location updates.
Issue #26: Switch to the relevant location data source.

When Google Play Services is enabled or disabled
Issue #26: Corrections in GmsDeviceLocationDataSource

Register for location updates in onCreate.  Set fastest interval instead of interval
Issue #26: Cleanup in *DeviceLocationDataSource classes.
Issue #26: if the user wants high location accuracy, make sure the gps and/or network providers are enabled
Issue #26: translated location-related strings into es and fr