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/ndn-l3-protocol.cc b/model/ndn-l3-protocol.cc
index 272e445..59993ac 100644
--- a/model/ndn-l3-protocol.cc
+++ b/model/ndn-l3-protocol.cc
@@ -68,7 +68,6 @@
   return s_dataCounter;
 }
 
-
 TypeId
 L3Protocol::GetTypeId (void)
 {
@@ -84,7 +83,7 @@
   return tid;
 }
 
-L3Protocol::L3Protocol()
+L3Protocol::L3Protocol ()
 : m_faceCounter (0)
 {
   NS_LOG_FUNCTION (this);