Support VC references in VC builder to fix #62

Change-Id: Iec84c12ade2f64e8bbbd3d42b9e52788a0fba3fe
diff --git a/dev/demo/vcdemo.js b/dev/demo/vcdemo.js
index 9bb67e2..a3957f3 100644
--- a/dev/demo/vcdemo.js
+++ b/dev/demo/vcdemo.js
@@ -48,6 +48,10 @@
                   "operation" : "operation:injection",
                 }
               ]
+            },
+            {
+              "@type":"koral:docGroupRef",
+              "ref":"@kalamar/myCorpus"
             }
           ]
         }
@@ -122,7 +126,8 @@
       ['title', 'string'],
       ['subTitle', 'string'],
       ['pubDate', 'date'],
-      ['author', 'text']
+      ['author', 'text'],
+      ['@referTo', 'ref']
     ]).fromJson(json);
 
     document.getElementById('vc-view').appendChild(vc.element());