Adding support of more fields in ContentObject

All big fields (digest, signature, etc.) are represented with 32-bit
integers. Should be enough for simulation purposes.

Also. This commit contains a number of code reorganizations, so the code
may not work...
diff --git a/helper/ccnx-decoding-helper.cc b/helper/ccnx-decoding-helper.cc
index ee3f084..6d1d7c8 100644
--- a/helper/ccnx-decoding-helper.cc
+++ b/helper/ccnx-decoding-helper.cc
@@ -21,10 +21,8 @@
 #include "ccnx-decoding-helper.h"
 
 #include "ns3/ccnx-interest-header.h"
-#include "ns3/ccnx-content-object-header.h"
 
 #include "ccnb-parser/visitors/ccnb-parser-interest-visitor.h"
-#include "ccnb-parser/visitors/ccnb-parser-content-object-visitor.h"
 
 #include "ccnb-parser/syntax-tree/ccnb-parser-block.h"
 #include "ccnb-parser/syntax-tree/ccnb-parser-dtag.h"
@@ -47,16 +45,16 @@
   return i.GetDistanceFrom (start);
 }
 
-size_t
-CcnxDecodingHelper::Deserialize (Buffer::Iterator start, CcnxContentObjectHeader &contentObject)
-{
-  static CcnbParser::ContentObjectVisitor contentObjectVisitor;
+// size_t
+// CcnxDecodingHelper::Deserialize (Buffer::Iterator start, CcnxContentObjectHeader &contentObject)
+// {
+//   static CcnbParser::ContentObjectVisitor contentObjectVisitor;
 
-  Buffer::Iterator i = start;
-  Ptr<CcnbParser::Block> root = CcnbParser::Block::ParseBlock (i);
-  root->accept (contentObjectVisitor, &contentObject);
+//   Buffer::Iterator i = start;
+//   Ptr<CcnbParser::Block> root = CcnbParser::Block::ParseBlock (i);
+//   root->accept (contentObjectVisitor, &contentObject);
 
-  return i.GetDistanceFrom (start);
-}
+//   return i.GetDistanceFrom (start);
+// }
 
 } // namespace ns3