SetupWizard: Add option to apply default theme if one exists

* A bunch of code cleanup/refactoring to make this work

Change-Id: I059fb5fa5bcd7dd8821e993218a320554f10a314
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index e8f2b0c..51490e8 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -77,6 +77,7 @@
                   android:launchMode="singleInstance"
                   android:excludeFromRecents="true"
                   android:uiOptions="none"
+                  android:configChanges="themeChange|mcc|mnc"
                   android:immersive="true">
 
             <intent-filter android:priority="9">