graying corpus statistic(plus tests+vc test fixed) and fix vc serialization

Change-Id: I3f934c2cc0ebbb0a91b5fa8f529bf3f5c3ebd391
(cherry picked from commit 172d6a4bbc7d29a0fe7c23b114fbbf485e2f4aeb)
diff --git a/dev/js/src/vc/jsonld.js b/dev/js/src/vc/jsonld.js
index 600a5bb..21260d4 100644
--- a/dev/js/src/vc/jsonld.js
+++ b/dev/js/src/vc/jsonld.js
@@ -99,6 +99,10 @@
       return null;
     },
 
+    incomplete : function () {
+      return false;
+    },
+
     toQuery : function () {
       return '';
     }