Add indexing for ListPreferences

- now support ListPreferences and save the "entries" attribute
- update Index database schema (and increment its version)
- do some clever stuff when showing Search results: if there is
a "$s" or "%s" in the summary (replacement strings), just use
the entries instead

Change-Id: If36595c3816706b6349faff7d3c2e725d3ea33f4

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

@@ -31,6 +31,7 @@ public class SearchIndexableRaw extends SearchIndexableData {
     public String title;
     public String summaryOn;
     public String summaryOff;
+    public String entries;
     public String keywords;
 
     public String screenTitle;