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/accounts/AddAccountSettings.java

@@ -31,6 +31,7 @@ import android.util.Log;
 import android.widget.Toast;
 
 import com.android.settings.R;
+import com.android.settings.Settings;
 import com.android.settings.Utils;
 
 import java.io.IOException;
@@ -142,7 +143,7 @@ public class AddAccountSettings extends Activity {
                 getIntent().getStringArrayExtra(AccountPreferenceBase.AUTHORITIES_FILTER_KEY);
         final String[] accountTypes =
                 getIntent().getStringArrayExtra(AccountPreferenceBase.ACCOUNT_TYPES_FILTER_KEY);
-        final Intent intent = new Intent(this, ChooseAccountActivity.class);
+        final Intent intent = new Intent(this, Settings.ChooseAccountActivity.class);
         if (authorities != null) {
             intent.putExtra(AccountPreferenceBase.AUTHORITIES_FILTER_KEY, authorities);
         }