src: Changing namespace ndn to namespace nfd

Also, this commit imports used classes from ::ndn namespace (from
NDN-CPP library) directly to ::nfd namespace.

refs: #1163

Change-Id: I9cc9d72e00af495b4ed0c84e6d418a7c9ba986cb
diff --git a/daemon/table/pit.hpp b/daemon/table/pit.hpp
index 44dc252..9dd2e1e 100644
--- a/daemon/table/pit.hpp
+++ b/daemon/table/pit.hpp
@@ -8,7 +8,7 @@
 #define NFD_TABLE_PIT_HPP
 
 #include "pit-entry.hpp"
-namespace ndn {
+namespace nfd {
 namespace pit {
 
 /** \class DataMatchResult
@@ -52,6 +52,6 @@
   std::list<shared_ptr<pit::Entry> > m_table;
 };
 
-} // namespace ndn
+} // namespace nfd
 
 #endif // NFD_TABLE_PIT_HPP