Implementing content store using Boost.MultiIndex container

Adding .SetGroupName("Ccnx") call to Ccnx-related objects (probably
missed some).  This call is advisory, but it is nice to give users
information about Ccnx-related objects (this information is accessible
via --PrintGroup=Ccnx command line argument)
diff --git a/model/ccnx-l3-protocol.h b/model/ccnx-l3-protocol.h
index 145051f..6167fd0 100644
--- a/model/ccnx-l3-protocol.h
+++ b/model/ccnx-l3-protocol.h
@@ -41,7 +41,8 @@
 class Header;
 class CcnxInterestHeader;
 class CcnxContentObjectHeader;
-  
+class CcnxContentStore;
+
 /**
  * \ingroup ccnx
  * \brief Actual implementation of the Ccnx network layer
@@ -160,15 +161,25 @@
   Ptr<Node> m_node; ///< \brief node on which ccnx stack is installed
   Ptr<CcnxForwardingStrategy> m_forwardingStrategy; ///< \brief smart pointer to the selected forwarding strategy
 
-  // TracedCallback<Ptr<const Packet>, Ptr<const CcnxFace> > m_sendOutgoingTrace;
-  // TracedCallback<Ptr<const Packet>, Ptr<const CcnxFace> > m_unicastForwardTrace;
-  // TracedCallback<Ptr<const Packet>, Ptr<const CcnxFace> > m_localDeliverTrace;
+  Ptr<CcnxContentStore> m_contentStore;
+  
+  /**
+   * \brief Trace of transmitted packets, including all headers
+   * \internal
+   */
+  TracedCallback<Ptr<const Packet>, Ptr<Ccnx>, Ptr<const CcnxFace> > m_txTrace;
 
-  // // The following two traces pass a packet with an IP header
-  // TracedCallback<Ptr<const Packet>, Ptr<Ccnx>, Ptr<const CcnxFace> > m_txTrace;
-  // TracedCallback<Ptr<const Packet>, Ptr<Ccnx>, Ptr<const CcnxFace> > m_rxTrace;
-  // // <ip-header, payload, reason, ifindex> (ifindex not valid if reason is DROP_NO_ROUTE)
-  // TracedCallback<Ptr<const Packet>, DropReason, Ptr<const Ccnx>, Ptr<const CcnxFace> > m_dropTrace;
+  /**
+   * \brief Trace of received packets, including all headers
+   * \internal
+   */
+  TracedCallback<Ptr<const Packet>, Ptr<Ccnx>, Ptr<const CcnxFace> > m_rxTrace;
+
+  /**
+   * \brief Trace of dropped packets, including reason and all headers
+   * \internal
+   */
+  TracedCallback<Ptr<const Packet>, DropReason, Ptr<const Ccnx>, Ptr<const CcnxFace> > m_dropTrace;
 };
   
 } // Namespace ns3