NzbDrone v1533 - Added SPK compatibility for built-in NzbDrone updates!

SPK now versioned by date for multi-branch and built-in NzbDrone updater compatibility - SPK upgrade now retains current NzbDrone binary (avoids potential binary downgrade) when necessary
I'm not sure if you're agreeing with me or not, @Diaoul? :) 
The package downloads 2.0.0.1533, but because NzbDrone can update itself, that version won't be correct for very long. That's the reason for the date (release date for the package maybe? Don't know for sure)