Add Indexable.SearchIndexProvider.getNonIndexableKeys(Context)

- getNonIndexableKeys(Context) allow a SearchIndexProvider to tell which data
he does not want to index by providing a list of the data keys
- use this new API for SoundSettings and removing KEY_EMERGENCY_TONE related
settings if the device is not CDMA
- add a BaseSearchIndexProvider for code simplification

Change-Id: I23633ace1d7e390ee05fac0a5458a33e04e72d8d

src/com/android/settings/search/Indexable.java

@@ -57,5 +57,13 @@ public interface Indexable {
          * @return a list of {@link SearchIndexableRaw} references. Can be null.
          */
         List<SearchIndexableRaw> getRawDataToIndex(Context context, boolean enabled);
+
+        /**
+         * Return a list of data keys that cannot be indexed. See {@link SearchIndexableRaw}
+         *
+         * @param context the context.
+         * @return a list of {@link SearchIndexableRaw} references. Can be null.
+         */
+        List<String> getNonIndexableKeys(Context context);
     }
 }