NightLight: reworked settings, defined fade duration and simplified service.

shell.qml

@@ -103,7 +103,10 @@ ShellRoot {
     // Save a ref. to our lockScreen so we can access it  easily
     PanelService.lockScreen = lockScreen
 
-    // Ensure our singleton is created as soon as possible so we start fetching weather asap
+    // Ensure our location singleton is created as soon as possible so we start fetching weather asap
     LocationService.init()
+
+    // Kickoff NightLight service
+    NightLightService.apply()
   }
 }