model: Another set of refactoring/renaming to make code compile (not tested yet)

Refs #1005 (http://redmine.named-data.net/)
diff --git a/examples/custom-apps/custom-app.h b/examples/custom-apps/custom-app.h
index 0d33bd8..ed21a2c 100644
--- a/examples/custom-apps/custom-app.h
+++ b/examples/custom-apps/custom-app.h
@@ -54,12 +54,11 @@
 
   // (overridden from ndn::App) Callback that will be called when Interest arrives
   virtual void
-  OnInterest (const Ptr<const ndn::Interest> &interest, Ptr<Packet> origPacket);
+  OnInterest (Ptr<const ndn::Interest> interest);
 
   // (overridden from ndn::App) Callback that will be called when Data arrives
   virtual void
-  OnContentObject (const Ptr<const ndn::ContentObject> &contentObject,
-                   Ptr<Packet> payload);
+  OnContentObject (Ptr<const ndn::ContentObject> contentObject);
 
 private:
   void