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/deviceinfo/Memory.java

@@ -40,7 +40,6 @@ import android.os.storage.StorageEventListener;
 import android.os.storage.StorageManager;
 import android.os.storage.StorageVolume;
 import android.preference.Preference;
-import android.preference.PreferenceActivity;
 import android.preference.PreferenceScreen;
 import android.util.Log;
 import android.view.Menu;
@@ -49,6 +48,7 @@ import android.view.MenuItem;
 import android.widget.Toast;
 
 import com.android.settings.R;
+import com.android.settings.SettingsActivity;
 import com.android.settings.SettingsPreferenceFragment;
 import com.android.settings.Utils;
 import com.google.android.collect.Lists;
@@ -186,8 +186,8 @@ public class Memory extends SettingsPreferenceFragment {
     public boolean onOptionsItemSelected(MenuItem item) {
         switch (item.getItemId()) {
             case R.id.storage_usb:
-                if (getActivity() instanceof PreferenceActivity) {
-                    ((PreferenceActivity) getActivity()).startPreferencePanel(
+                if (getActivity() instanceof SettingsActivity) {
+                    ((SettingsActivity) getActivity()).startPreferencePanel(
                             UsbSettings.class.getCanonicalName(),
                             null,
                             R.string.storage_title_usb, null,