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/ethernet-channel.hpp b/daemon/face/ethernet-channel.hpp
index 510b7aa..2096585 100644
--- a/daemon/face/ethernet-channel.hpp
+++ b/daemon/face/ethernet-channel.hpp
@@ -32,8 +32,7 @@
 
 #include <ndn-cxx/net/network-interface.hpp>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 /**
  * \brief Class implementing Ethernet-based channel to create faces
@@ -137,7 +136,6 @@
 #endif
 };
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_ETHERNET_CHANNEL_HPP