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/tcp-transport.hpp b/daemon/face/tcp-transport.hpp
index 950d850..595e574 100644
--- a/daemon/face/tcp-transport.hpp
+++ b/daemon/face/tcp-transport.hpp
@@ -28,8 +28,7 @@
 
 #include "stream-transport.hpp"
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_MEMBER_DECL_SPECIALIZED(StreamTransport<boost::asio::ip::tcp>);
 
@@ -99,7 +98,6 @@
   time::milliseconds m_nextReconnectWait;
 };
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_TCP_TRANSPORT_HPP