Upgrade the underlying NFD and ndn-cxx to version 0.6.0

Compilation is currently broken and is fixed in the following commit

Change-Id: Ic0dba06a9afd66a810172d4a512f35f6df6b25a2
Refs: #4306
diff --git a/utils/tracers/ndn-l3-tracer.hpp b/utils/tracers/ndn-l3-tracer.hpp
index 15dd41f..6b0fafe 100644
--- a/utils/tracers/ndn-l3-tracer.hpp
+++ b/utils/tracers/ndn-l3-tracer.hpp
@@ -21,16 +21,11 @@
 #define NDN_L3_TRACER_H
 
 #include "ns3/ndnSIM/model/ndn-common.hpp"
+#include "ns3/ndnSIM/NFD/daemon/table/pit-entry.hpp"
 
 #include "ns3/ptr.h"
 #include "ns3/simple-ref-count.h"
 
-namespace nfd {
-namespace pit {
-class Entry;
-} // namespace pit
-} // namespace nfd
-
 namespace ns3 {
 
 class Node;