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/multicast-ethernet-transport.cpp b/daemon/face/multicast-ethernet-transport.cpp
index 5d34846..2068012 100644
--- a/daemon/face/multicast-ethernet-transport.cpp
+++ b/daemon/face/multicast-ethernet-transport.cpp
@@ -43,8 +43,7 @@
 #endif
 #endif
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_INIT(MulticastEthernetTransport);
 
@@ -146,5 +145,4 @@
   NDN_THROW(Error("Failed to join multicast group"));
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face