Moving around path weight tagging. Now CcnxFace owns metric field, which is used for tagging.

Correcting bugs in blackhole-sprint scenario.  This time it should be
the right one:
- instead of a hijacker app, all faces on hijacked node are turned down
- there was a trick with RTT estimation (when batch, it is necessary to
  reset history upon a new batch)
- instead of random runs, trying all possible combinations of
  producer/hijacker
diff --git a/helper/tracers/ccnx-path-weight-tracer.h b/helper/tracers/ccnx-path-weight-tracer.h
index 868e61f..f4bd187 100644
--- a/helper/tracers/ccnx-path-weight-tracer.h
+++ b/helper/tracers/ccnx-path-weight-tracer.h
@@ -35,7 +35,7 @@
 class CcnxPathWeightTracer : public SimpleRefCount<CcnxPathWeightTracer>
 {
 public:
-  CcnxPathWeightTracer (std::ostream &os, Ptr<Node> node, std::string appId);
+  CcnxPathWeightTracer (std::ostream &os, Ptr<Node> node);
   virtual ~CcnxPathWeightTracer () { };
 
   void
@@ -55,7 +55,6 @@
   std::ostream &m_os;
   std::string m_node;
   Ptr<Node> m_nodePtr;
-  std::string m_appId;
 };
 
 } // namespace ns3