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-factory.cpp b/daemon/face/ethernet-factory.cpp
index 4fea598..59f0c5c 100644
--- a/daemon/face/ethernet-factory.cpp
+++ b/daemon/face/ethernet-factory.cpp
@@ -30,8 +30,7 @@
 #include <boost/range/adaptors.hpp>
 #include <boost/range/algorithm/copy.hpp>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_INIT(EthernetFactory);
 NFD_REGISTER_PROTOCOL_FACTORY(EthernetFactory);
@@ -377,5 +376,4 @@
   }
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face