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/wifi/WifiPickerActivity.java

@@ -16,7 +16,6 @@
 package com.android.settings.wifi;
 
 import com.android.settings.ButtonBarHandler;
-import com.android.settings.ChooseLockGeneric.ChooseLockGenericFragment;
 import com.android.settings.wifi.p2p.WifiP2pSettings;
 
 import android.app.Fragment;
@@ -54,8 +53,8 @@ public class WifiPickerActivity extends PreferenceActivity implements ButtonBarH
 
     /**
      * Almost dead copy of
-     * {@link PreferenceActivity#startWithFragment(String, Bundle, Fragment, int)}, except
-     * this has additional codes for button bar handling.
+     * {@link PreferenceActivity#startWithFragment(String, Bundle, Fragment, int)}, except this has
+     * additional codes for button bar handling.
      */
     @Override
     public void startWithFragment(String fragmentName, Bundle args,