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/scheduler.cpp b/daemon/core/scheduler.cpp
index c4fc1d8..f9f9996 100644
--- a/daemon/core/scheduler.cpp
+++ b/daemon/core/scheduler.cpp
@@ -6,7 +6,7 @@
 
 #include "scheduler.hpp"
 
-namespace ndn {
+namespace nfd {
 
 struct EventIdImpl
 {
@@ -173,4 +173,4 @@
 }
 
 
-} // namespace ndn
+} // namespace nfd