Allow users to choose a notification assistant.

Change-Id: Iddfbfedbb6a3aae246058ff41324dc06852484cb

src/com/android/settings/Settings.java

@@ -121,6 +121,7 @@ public class Settings extends SettingsActivity {
     public static class WriteSettingsActivity extends SettingsActivity { /* empty */ }
     public static class AppDrawOverlaySettingsActivity extends SettingsActivity { /* empty */ }
     public static class AppWriteSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class ManageDefaultAppsActivity extends SettingsActivity { /* empty */ }
 
     // Categories.
     public static class WirelessSettings extends SettingsActivity { /* empty */ }