Bump to v6.0.2 for release.
Merge branch 'master' into next
Guard against race condition when querying for active VI.

I have a hunch this will fix a NullPointerException thrown from the
VehicleService when calling VehicleManager.getActiveVehicleInterface
(see
https://bugsnag.com/openxc/openxc-android-app/errors/546bde13f32e0785726662a5?event_id=546bde134758e1c6050291ef#stacktrace).
Use an explicit intent to start VehicleService.

All along, just had to get the names matched up - I was trying to
start VehicleServiceInterface instead of just VehicleService.

This should fix this illegal argument exception crash: https://bugsnag.com/openxc/openxc-android-app/errors/546a6e1af32e078572623111
Don't try and render date if a message isn't timestampped.

Fixed #206.
Bump to v6.0.3 for release.