Add revertOf to ChangeIndex

This change adds revertOf to the ChangeIndex and adds a predicate to query
the new propery.

Change-Id: I40684400ab8fa1d854dc70af5e76214222581d07

gerrit-gwtui/src/main/java/com/google/gerrit/client/SearchSuggestOracle.java

@@ -154,6 +154,8 @@ public class SearchSuggestOracle extends HighlightSuggestOracle {
 
     suggestions.add("unresolved:");
 
+    suggestions.add("revertof:");
+
     if (Gerrit.isNoteDbEnabled()) {
       suggestions.add("cc:");
       suggestions.add("hashtag:");