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/nfc/AndroidBeam.java

@@ -21,16 +21,14 @@ import android.app.Activity;
 import android.app.Fragment;
 import android.nfc.NfcAdapter;
 import android.os.Bundle;
-import android.os.Handler;
-import android.preference.PreferenceActivity;
 import android.view.Gravity;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.CompoundButton;
-import android.widget.ImageView;
 import android.widget.Switch;
 import com.android.settings.R;
+import com.android.settings.SettingsActivity;
 
 public class AndroidBeam extends Fragment
         implements CompoundButton.OnCheckedChangeListener {
@@ -46,7 +44,7 @@ public class AndroidBeam extends Fragment
 
         mActionBarSwitch = new Switch(activity);
 
-        if (activity instanceof PreferenceActivity) {
+        if (activity instanceof SettingsActivity) {
             final int padding = activity.getResources().getDimensionPixelSize(
                     R.dimen.action_bar_switch_padding);
             mActionBarSwitch.setPaddingRelative(0, 0, padding, 0);