Use AppCompatContactsActivity as super class of activities (1/3)

- AppCompatContactsActivity will replace ContactsActivity eventually

- modified PeopleActivity and ContactSelectionActivity

- fixed the color of buttons in contacts_unavailable_fragment_content on K

Bug: 25629359
Change-Id: I7312fb446c6affc070db1b44b74ed857afcf8f3a
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index e5d3427..9014b10 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -61,7 +61,7 @@
         <!-- The main Contacts activity with the contact list, favorites, and groups. -->
         <activity android:name=".activities.PeopleActivity"
             android:label="@string/launcherActivityLabel"
-            android:theme="@style/PeopleTheme"
+            android:theme="@style/PeopleActivityTheme"
             android:clearTaskOnLaunch="true"
             android:launchMode="singleTop"
             android:resizeableActivity="true"