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/unicast-ethernet-transport.cpp b/daemon/face/unicast-ethernet-transport.cpp
index 853ca55..3da0681 100644
--- a/daemon/face/unicast-ethernet-transport.cpp
+++ b/daemon/face/unicast-ethernet-transport.cpp
@@ -28,8 +28,7 @@
 
 #include <cstdio>   // for snprintf()
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_INIT(UnicastEthernetTransport);
 
@@ -100,5 +99,4 @@
   setExpirationTime(time::steady_clock::now() + m_idleTimeout);
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face