model: Major API changes

Interest and ContentObject are no longer derived from Header class.
Instead, they are encapsulating payload and, optionally, wire-formatted
Packet object.

Refs #1005 (http://redmine.named-data.net/)
diff --git a/model/fw/best-route.h b/model/fw/best-route.h
index f7caa19..6648acb 100644
--- a/model/fw/best-route.h
+++ b/model/fw/best-route.h
@@ -58,8 +58,7 @@
   // from super
   virtual bool
   DoPropagateInterest (Ptr<Face> incomingFace,
-                       Ptr<const Interest> header,
-                       Ptr<const Packet> origPacket,
+                       Ptr<const Interest> interest,
                        Ptr<pit::Entry> pitEntry);
 protected:
   static LogComponent g_log;