docs: Documentation update, initial preparation for version 2.1 release

Change-Id: I3694a8791b9540fc1b926a83ff55421b47e0f1e2
diff --git a/model/ndn-common.hpp b/model/ndn-common.hpp
index dbb1502..237fc3e 100644
--- a/model/ndn-common.hpp
+++ b/model/ndn-common.hpp
@@ -63,7 +63,10 @@
 using ::ndn::Block;
 using ::ndn::KeyChain;
 
+#ifndef DOXYGEN
+// For python bindings
 namespace nfd = ::nfd;
+#endif // DOXYGEN
 
 } // namespace ndn
 } // namespace ns3