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/fib-nexthop.hpp b/daemon/table/fib-nexthop.hpp
index c3e2cf0..5961b42 100644
--- a/daemon/table/fib-nexthop.hpp
+++ b/daemon/table/fib-nexthop.hpp
@@ -10,7 +10,7 @@
 #include "common.hpp"
 #include "face/face.hpp"
 
-namespace ndn {
+namespace nfd {
 namespace fib {
 
 /** \class NextHop
@@ -38,6 +38,6 @@
 };
 
 } // namespace fib
-} // namespace ndn
+} // namespace nfd
 
 #endif // NFD_TABLE_FIB_NEXTHOP_HPP