Update fingerprint settings to spec

- Make it look like a sub settings activity, with back button
- Add disclaimer to describe what your fingerprint can be used for
- Update visuals and text for "Add fingerprint"
- Update related string

Bug: 20594955
Change-Id: I0adfcc743db386e0abf9cfdafff3d068ebc3b4bc

res/layout/fingerprint_settings_footer.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2015 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
+  -->
+<TextView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    style="@android:style/TextAppearance.Material.Body1"
+    android:layout_width="wrap_content"
+    android:layout_height="wrap_content"
+    android:textColor="?android:attr/textColorSecondary"
+    android:paddingTop="32dp"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:selectable="false">
+</TextView>