Fix a few problems identified by Android Lint.
Add a little more delay to a makeground test more consistent.
Only poll native GPS if connected to a vehicle.

Instead of creating the NativeLocationSource in the VehicleManager's
process, it is created in the VehicleService process - this allows it to
be notified when vehicle interfaces are connected and disconnected, so
it can know when to stop waiting for GPS updates from Android.

Fixed #128
Decrease max ram for JVM in the hope of making Travis CI work better.