Modification of CcnxFace interface and unification of CCNx applications via common CcnxApp class

Moving functionality of interest limits from PIT to Face.

!!! Code compiles, but probably doesn't work !!!
diff --git a/model/ccnx-forwarding-strategy.h b/model/ccnx-forwarding-strategy.h
index b8bbc5b..d7a5ab5 100644
--- a/model/ccnx-forwarding-strategy.h
+++ b/model/ccnx-forwarding-strategy.h
@@ -42,10 +42,6 @@
 class CcnxForwardingStrategy : public Object
 {
 public:
-  typedef
-  Callback<void, const Ptr<CcnxFace> &, const Ptr<const CcnxInterestHeader> &, const Ptr<Packet> &>
-  SendCallback;
-
   static TypeId GetTypeId (void);
 
   /**
@@ -69,8 +65,7 @@
   PropagateInterest (const CcnxPitEntry  &pitEntry, 
                      const Ptr<CcnxFace> &incomingFace,
                      Ptr<CcnxInterestHeader> &header,
-                     const Ptr<const Packet> &packet,
-                     SendCallback sendCallback) = 0;
+                     const Ptr<const Packet> &packe) = 0;
     
   /**
    * @brief Set link to PIT for the forwarding strategy