[ThemePicker] Add bottom navbar to main activity

Set up the basic layout and add a bottom nav bar to
CustomizationPickerActivity, with basic support for
switching between section fragments.
(Fragments to be added in a separate CL)

Bug: 120560581
Change-Id: I06832260d20ca2938b6c04e110fadf45bc3070a2
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 7610e13..da3d15e 100755
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -8,14 +8,14 @@
         android:hardwareAccelerated="true"
         android:icon="@mipmap/product_logo_wallpapers_launcher_color_48"
         android:label="@string/app_name"
-        android:theme="@style/WallpaperTheme"
+        android:theme="@style/CustomizationTheme"
         android:requiredForAllUsers="true"
         android:restoreAnyVersion="true"
         android:supportsRtl="true">
 
         <activity android:name="com.android.theme.picker.ThemePickerActivity"
             android:label="@string/app_name"
-            android:theme="@style/WallpaperTheme"
+            android:theme="@style/CustomizationTheme.NoActionBar"
             android:resizeableActivity="true">
             <intent-filter>
                 <action android:name="android.intent.action.SET_WALLPAPER"/>