ONOS-1479 - GUI Topology Overlay Work - (WIP)
- UiExtension now uses Builder Pattern; added topology overlay factory.
- Refactored UiExtensionTest (and other classes) to use builder.
- Created UiTopoOverlayFactory, UiTopoOverlay, and TopoOverlayCache.
- Started implementation of TrafficOverlay.
- Inject TopoOverlayCache into TopologyViewMessageHandler; added TopoSelectOverlay request handler.
- Modified UiExtensionManager to create traffic overlay.
- Augmented UiWebSocket to create overlays on demand, and inject overlay cache into topo view message handler.
- added client side wiring to switch overlays.

Change-Id: I6f99596aefb3b87382517ce929d268a2447545ee
diff --git a/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java b/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
index b3782a2..e27f5d9 100644
--- a/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
+++ b/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
@@ -107,8 +107,9 @@
     void exec(String eventType, long sid, ObjectNode payload) {
         RequestHandler requestHandler = handlerMap.get(eventType);
         if (requestHandler != null) {
-            log.debug("process {} event...", eventType);
             requestHandler.process(sid, payload);
+        } else {
+            log.warn("no request handler for event type {}", eventType);
         }
     }