model: Another major change: switching to NDN.cxx API for ndn::Name

NDN.cxx code is almost exactly the same, with minor NS-3 specific customizations

Refs #1011 (http://redmine.named-data.net/issues/1011)
diff --git a/apps/ndn-producer.cc b/apps/ndn-producer.cc
index 130b450..e8a66aa 100644
--- a/apps/ndn-producer.cc
+++ b/apps/ndn-producer.cc
@@ -129,7 +129,7 @@
 
   Ptr<ContentObject> data = Create<ContentObject> (Create<Packet> (m_virtualPayloadSize));
   Ptr<Name> dataName = Create<Name> (interest->GetName ());
-  dataName->Append (m_postfix);
+  dataName->append (m_postfix);
   data->SetName (dataName);
   data->SetFreshness (m_freshness);