Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/daemon/face/stream-transport.hpp b/daemon/face/stream-transport.hpp
index c4ae849..ec33b26 100644
--- a/daemon/face/stream-transport.hpp
+++ b/daemon/face/stream-transport.hpp
@@ -32,8 +32,7 @@
 
 #include <queue>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 /** \brief Implements Transport for stream-based protocols.
  *
@@ -333,7 +332,6 @@
   return m_sendQueueBytes;
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_STREAM_TRANSPORT_HPP