Redesign settings for tablets

1. Move AppCompatPreferenceActivity from Dialer to ContactsCommon
2. Move ContactsPreferenceActivity from Contacts to ContactsCommon,
   make it extend AppCompatPreferenceActivity and avoid building
   headers (by not overriding onBuildHeaders)
3. Move the "About" PreferenceScreen to preference_about.xml and
   add AboutPreferenceFragment so that we could switch between two
   fragments.
2. Add "back button" to LicenseActivity.

Here's how it looks:
https://docs.google.com/a/google.com/presentation/d/1A5n2o8epBCrizZvbOyelvjoHz-s5-IRlJd-KqWAMBao/edit?usp=sharing

Bug: 25629359
Bug: 26469731
Change-Id: If88722a62e41d1a2f4f70939b2d52d697e204628
diff --git a/res-common/values/strings.xml b/res-common/values/strings.xml
index ef7dbc7..0ced780 100644
--- a/res-common/values/strings.xml
+++ b/res-common/values/strings.xml
@@ -678,6 +678,9 @@
     <!-- Label of the "About" setting -->
     <string name="setting_about">About Contacts</string>
 
+    <!-- Title of the settings activity [CHAR LIMIT=64] -->
+    <string name="activity_title_settings">Settings</string>
+
     <!-- Action that shares visible contacts -->
     <string name="share_visible_contacts">Share visible contacts</string>