Highlight row (instead of ripple) when come from search.

- Moved HighlightableAdapter to its own class
- Replaced ripple with blue background
- Bluebackground only stays for 5 seconds. After that it's replaced by
  ?attr/selectableBackground

Misc fixes.

- Fix NPE in UserSettings
- Update char limit on a new string

Change-Id: I4687e54e71fd7b9243f520b7630563df58be23d4
Fixes: 71715698
Fixes: 72761974
Test: robotests

res/color/preference_highligh_color.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2018 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.
+  -->
+
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:alpha="0.1" android:color="?android:attr/colorAccent" />
+</selector>