Add the automatic handling of night/notnight UI modes.

The automatic switching between night/notnight is based on the calulcation of
the civil twilight of the current location. The location is mainly retrieved
from the NetworkLocationProvider.

Automatic switching will only be available, when
1) the device is in UI_MODE_TYPE_CAR
2) the setting for the UI mode are set to 'automatic'

If mode is set to automatic, the next twilight is caluclated and
an alarm is set that timestamp. The alarm will trigger a new calculation
of the twilight and sets the UI_MODE_NIGHT to the appropriate value.

	modified:   services/java/com/android/server/DockObserver.java
	new file:   services/java/com/android/server/TwilightCalculator.java