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

res/xml/device_info_settings.xml

@@ -35,10 +35,8 @@
         <!-- Device status - launches activity -->
         <PreferenceScreen android:key="status_info"
                 android:title="@string/device_status" 
-                android:summary="@string/device_status_summary">
-            <intent android:action="android.intent.action.MAIN"
-                    android:targetPackage="com.android.settings"
-                    android:targetClass="com.android.settings.deviceinfo.Status" />
+                android:summary="@string/device_status_summary"
+                android:fragment="com.android.settings.deviceinfo.Status">
         </PreferenceScreen>
 
         <!-- Legal Information -->

res/xml/settings_headers.xml

@@ -22,6 +22,13 @@
     <header android:id="@+id/wireless_section"
         android:title="@string/header_category_wireless_networks" />
 
+    <!-- Dashboard -->
+    <!--TODO: android:icon="@drawable/ic_settings_dashboard"-->
+    <header
+        android:id="@+id/dashboard"
+        android:fragment="com.android.settings.dashboard.DashboardSummary"
+        android:title="@string/dashboard_title" />
+
     <!-- Wifi -->
     <header
         android:id="@+id/wifi_settings"