Fix bug #15335840 "Safety information" search suggestion shown though

..."Safety information" setting is not available in settings app

- implement a SearchIndexProvider for DeviceInfoSettings and
remove some Preference indexing depending on the device state
and configuration
- remove old non used Preferences
- some code cleaning

Change-Id: I3b2c9dc7cb9f1137b553fed9330aeea4020bd2f8

res/xml/device_info_settings.xml

@@ -80,15 +80,6 @@
             <intent android:action="android.settings.SAFETY" />
         </PreferenceScreen>
 
-        <!-- Contributors -->
-        <!-- 
-        <PreferenceScreen
-                android:key="contributors"
-                android:title="@string/contributors_title">
-            <intent android:action="android.settings.TEAM" />
-        </PreferenceScreen>
-        -->
-
         <PreferenceScreen
                 android:key="regulatory_info"
                 android:title="@string/regulatory_information">