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-entry.cpp b/daemon/table/pit-entry.cpp
index e11abef..094ea6e 100644
--- a/daemon/table/pit-entry.cpp
+++ b/daemon/table/pit-entry.cpp
@@ -7,7 +7,7 @@
 #include "pit-entry.hpp"
 #include <algorithm>
 
-namespace ndn {
+namespace nfd {
 namespace pit {
 
 Entry::Entry(const Interest& interest)
@@ -93,4 +93,4 @@
 
 
 } // namespace pit
-} // namespace ndn
+} // namespace nfd