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/core/time.hpp b/daemon/core/time.hpp
index 3b0d002..5efd082 100644
--- a/daemon/core/time.hpp
+++ b/daemon/core/time.hpp
@@ -9,7 +9,7 @@
 
 #include "common.hpp"
 
-namespace ndn {
+namespace nfd {
 namespace time {
 
 class monotonic_clock;
@@ -156,6 +156,6 @@
 
 
 } // namespace time
-} // namespace ndn
+} // namespace nfd
 
 #endif // NFD_CORE_TIME_H