base: Interest and Data packets can now be tagged with arbitrary information

This functionality is similar to StrategyInfoHost and StrategyInfo in
NFD.  Current usage will include ndnSIM, where Interest and Data ndn-cxx
packets need to be associated with ns3::Packet data structures.

Change-Id: I313e4be0f4b6eac80f3824e3fd725968e265fdce
Refs: #2336
diff --git a/src/interest.hpp b/src/interest.hpp
index 1433628..9516454 100644
--- a/src/interest.hpp
+++ b/src/interest.hpp
@@ -30,6 +30,7 @@
 #include "selectors.hpp"
 #include "util/time.hpp"
 #include "management/nfd-local-control-header.hpp"
+#include "tag-host.hpp"
 
 namespace ndn {
 
@@ -42,7 +43,7 @@
 
 /** @brief represents an Interest packet
  */
-class Interest : public enable_shared_from_this<Interest>
+class Interest : public TagHost, public enable_shared_from_this<Interest>
 {
 public:
   class Error : public tlv::Error