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/WifiInfo.java

@@ -19,18 +19,17 @@ package com.android.settings.wifi;
 import com.android.settings.R;
 
 import android.os.Bundle;
-import android.preference.PreferenceActivity;
+import com.android.settings.SettingsPreferenceFragment;
 
 
 /**
  * Wifi information menu item on the diagnostic screen
  */
-public class WifiInfo extends PreferenceActivity {
+public class WifiInfo extends SettingsPreferenceFragment {
 
     @Override
-    protected void onCreate(Bundle savedInstanceState) {
+    public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         addPreferencesFromResource(R.xml.testing_wifi_settings);
     }
-
 }