Change in CcnxApp API.  Now callbacks also contain pointer of original
packet (useful to get packet tags, if they exist)

Reflecting changes in PackegTag API

Rescanning bindings

More work on packet-path-weight tracers
diff --git a/model/annotated-topology-reader.cc b/model/annotated-topology-reader.cc
index db8392d..345c2f5 100644
--- a/model/annotated-topology-reader.cc
+++ b/model/annotated-topology-reader.cc
@@ -112,7 +112,7 @@
   return m_nodes;
 }
 
-std::list<TopologyReader::Link>
+const std::list<TopologyReader::Link>&
 AnnotatedTopologyReader::GetLinks () const
 {
   return m_linksList;