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/layout/dashboard.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2014 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/dashboard"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView android:id="@+id/dash_text"
+              android:layout_width="wrap_content"
+              android:layout_height="wrap_content"
+              android:layout_gravity="center"
+              android:text="@string/dashboard_wip"
+            />
+
+</FrameLayout>

res/layout/settings_main.xml

@@ -0,0 +1,81 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/*
+** Copyright 2014, The Android Open Source Project
+**
+** Licensed under the Apache License, Version 2.0 (the "License");
+** you may not use this file except in compliance with the License.
+** You may obtain a copy of the License at
+**
+**     http://www.apache.org/licenses/LICENSE-2.0
+**
+** Unless required by applicable law or agreed to in writing, software
+** distributed under the License is distributed on an "AS IS" BASIS,
+** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+** See the License for the specific language governing permissions and
+** limitations under the License.
+*/
+-->
+
+<android.support.v4.widget.DrawerLayout
+        xmlns:android="http://schemas.android.com/apk/res/android"
+        android:id="@+id/drawer_layout"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent">
+
+    <LinearLayout
+              android:orientation="vertical"
+              android:layout_height="match_parent"
+              android:layout_width="match_parent">
+
+        <android.preference.PreferenceFrameLayout android:id="@+id/prefs"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:layout_weight="1"
+        />
+
+        <RelativeLayout android:id="@+id/button_bar"
+                        android:layout_height="wrap_content"
+                        android:layout_width="match_parent"
+                        android:layout_weight="0"
+                        android:visibility="gone">
+
+            <Button android:id="@+id/back_button"
+                    android:layout_width="150dip"
+                    android:layout_height="wrap_content"
+                    android:layout_margin="5dip"
+                    android:layout_alignParentStart="true"
+                    android:text="@*android:string/back_button_label"
+                    />
+            <LinearLayout
+                    android:orientation="horizontal"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:layout_alignParentEnd="true">
+
+                <Button android:id="@+id/skip_button"
+                        android:layout_width="150dip"
+                        android:layout_height="wrap_content"
+                        android:layout_margin="5dip"
+                        android:text="@*android:string/skip_button_label"
+                        android:visibility="gone"
+                        />
+
+                <Button android:id="@+id/next_button"
+                        android:layout_width="150dip"
+                        android:layout_height="wrap_content"
+                        android:layout_margin="5dip"
+                        android:text="@*android:string/next_button_label"
+                        />
+            </LinearLayout>
+        </RelativeLayout>
+
+    </LinearLayout>
+
+    <ListView android:id="@+id/headers_drawer"
+              android:layout_width="300dp"
+              android:layout_height="match_parent"
+              android:layout_gravity="start"
+              android:background="#ff333333"/>
+
+</android.support.v4.widget.DrawerLayout>