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-flooding-strategy.h b/model/ccnx-flooding-strategy.h
index 0d43b6a..8be12e9 100644
--- a/model/ccnx-flooding-strategy.h
+++ b/model/ccnx-flooding-strategy.h
@@ -50,8 +50,7 @@
   PropagateInterest (const CcnxPitEntry  &pitEntry, 
                      const Ptr<CcnxFace> &incomingFace,
                      Ptr<CcnxInterestHeader> &header,
-                     const Ptr<const Packet> &packet,
-                     SendCallback sendCallback);
+                     const Ptr<const Packet> &packet);
 };
     
 } //namespace ns3