model: First set of major API changes and reorganizations

Main motive: change interface in Face class, resulting in need to change forwarding strategy interfaces

Refs #1005 (http://redmine.named-data.net/)
diff --git a/model/ndn-app-face.h b/model/ndn-app-face.h
index 3a90f11..4b47fda 100644
--- a/model/ndn-app-face.h
+++ b/model/ndn-app-face.h
@@ -63,12 +63,11 @@
   
   ////////////////////////////////////////////////////////////////////
   // methods overloaded from Face
-  virtual void
-  RegisterProtocolHandler (ProtocolHandler handler);
-
-protected:
   virtual bool
-  SendImpl (Ptr<Packet> p);
+  SendInterest (Ptr<const Interest> interest, Ptr<const Packet> packet);
+
+  virtual bool
+  SendData (Ptr<const ContentObject> data, Ptr<const Packet> packet);
 
 public:
   virtual std::ostream&