Use Drawer in Settings app

- get rid of PreferenceActivity as much as we can and use fragments instead
- add Drawer widget
- add Dashboard high level entry into the Drawer (but this is work in progress and would be done in another CL)
- add bypass of fragment's Header  validation when launched from the Drawer but *force* validation if external
call thru an Intent

Be aware that WifiPickerActivity should remain for now a PreferenceActivity. It is used by SetupWizard and should
not trigger running the SettingsActivity's header building code. SetupWizard is a Home during the provisionnig process
and then deactivate itself as a Home but would make the Home header to appear in the Drawer (because momentarily we
would have two Home).

Also, verified that:

- the WiFi settings still work when called from SetupWizard
- when you have multiple Launchers, the Home header will appear in the list of Headers in the Drawer

Change-Id: I407a5e0fdd843ad7615d3d511c416a44e3d97c90

src/com/android/settings/MasterClear.java

@@ -31,7 +31,6 @@ import android.os.Environment;
 import android.os.SystemProperties;
 import android.os.UserManager;
 import android.preference.Preference;
-import android.preference.PreferenceActivity;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -115,7 +114,7 @@ public class MasterClear extends Fragment {
         preference.setFragment(MasterClearConfirm.class.getName());
         preference.setTitle(R.string.master_clear_confirm_title);
         preference.getExtras().putBoolean(ERASE_EXTERNAL_EXTRA, mExternalStorage.isChecked());
-        ((PreferenceActivity) getActivity()).onPreferenceStartFragment(null, preference);
+        ((SettingsActivity) getActivity()).onPreferenceStartFragment(null, preference);
     }
 
     /**