Show default app icon in default app screen.

- Renamed AdvancedAppSettings to DefaultAppSettings.
- Add logic to DefaultAppPreferenceController to also display icon.
- Modified DefautlAssistPrefController to suppress gear icon, and use
  the controller in default app setting UI to display icon.
- Remove dynamic injected payment setting activity and create the
  setting statically in xml.
- Add DefaultPaymentSettingsPreference to display default payment app
  title (no icon because we can't get it)

Change-Id: I6b8c768da0bafe5ec9a85ba9c79c7993b449be25
Fix: 36458534
Test: robotests

src/com/android/settings/nfc/PaymentBackend.java

@@ -42,7 +42,7 @@ public class PaymentBackend {
     }
 
     public static class PaymentAppInfo {
-        CharSequence label;
+        public CharSequence label;
         CharSequence description;
         Drawable banner;
         boolean isDefault;