Enabling app-layer tracing

Network-layer tracing is not working yet (needs a couple of attributes
to be implemented)
diff --git a/model/ccnx-face.h b/model/ccnx-face.h
index 0499abb..b63b1e7 100644
--- a/model/ccnx-face.h
+++ b/model/ccnx-face.h
@@ -47,11 +47,14 @@
  *
  * \see CcnxLocalFace, CcnxNetDeviceFace, CcnxIpv4Face, CcnxUdpFace
  */
-class CcnxFace  : public SimpleRefCount<CcnxFace>
+class CcnxFace  : public Object
 {
 public:
+  static TypeId
+  GetTypeId ();
+  
   /**
-   * \brief Ccnx protocol hanler
+   * \brief Ccnx protocol handler
    *
    * \param face Face from which packet has been received
    * \param packet Original packet