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

Refs #1005 (http://redmine.named-data.net/)
diff --git a/model/cs/content-store-with-freshness.h b/model/cs/content-store-with-freshness.h
index 3ba871c..22242b9 100644
--- a/model/cs/content-store-with-freshness.h
+++ b/model/cs/content-store-with-freshness.h
@@ -46,7 +46,7 @@
   Print (std::ostream &os) const;
 
   virtual inline bool
-  Add (Ptr<const ContentObject> header, Ptr<const Packet> packet);
+  Add (Ptr<const ContentObject> data);
 
 private:
   inline void
@@ -95,7 +95,7 @@
   bool ok = super::Add (data);
   if (!ok) return false;
 
-  NS_LOG_DEBUG (header->GetName () << " added to cache");
+  NS_LOG_DEBUG (data->GetName () << " added to cache");
   RescheduleCleaning ();
   return true;
 }