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/drawable/ic_add_24dp.xml

@@ -0,0 +1,24 @@
+<!--
+  ~ 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
+  -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24.0dp"
+        android:height="24.0dp"
+        android:viewportWidth="48.0"
+        android:viewportHeight="48.0">
+    <path
+        android:fillColor="?android:attr/colorAccent"
+        android:pathData="M38.0,26.0L26.0,26.0l0.0,12.0l-4.0,0.0L22.0,26.0L10.0,26.0l0.0,-4.0l12.0,0.0L22.0,10.0l4.0,0.0l0.0,12.0l12.0,0.0l0.0,4.0z"/>
+</vector>