Added mechanism for apps to easily add their own custom link/node/host highlighting wihout having to create a new UI extensions

Change-Id: Iefa21d76190c60db79a4b07a8b22e301d29fe58e
diff --git a/web/gui/src/main/java/org/onosproject/ui/impl/topo/Traffic2Monitor.java b/web/gui/src/main/java/org/onosproject/ui/impl/topo/Traffic2Monitor.java
index 76b9dc5..6a41cf2 100644
--- a/web/gui/src/main/java/org/onosproject/ui/impl/topo/Traffic2Monitor.java
+++ b/web/gui/src/main/java/org/onosproject/ui/impl/topo/Traffic2Monitor.java
@@ -65,6 +65,10 @@
     }
 
     @Override
+    protected void sendCustomTraffic() {
+    }
+
+    @Override
     protected void sendAllPortTrafficBits() {
         log.debug("TOPO-2-TRAFFIC: sendAllPortTrafficBits");
         msgHandler.sendHighlights(trafficSummary(TrafficLink.StatsType.PORT_STATS));