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/internal-transport.hpp b/daemon/face/internal-transport.hpp
index d729ecd..886af5c 100644
--- a/daemon/face/internal-transport.hpp
+++ b/daemon/face/internal-transport.hpp
@@ -30,8 +30,7 @@
 
 #include <ndn-cxx/transport/transport.hpp>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 /** \brief Abstracts a transport that can be paired with another.
  */
@@ -125,7 +124,6 @@
   signal::ScopedConnection m_fwTransportStateConn;
 };
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_INTERNAL_TRANSPORT_HPP