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/tcp-transport.cpp b/daemon/face/tcp-transport.cpp
index 466e2c6..0332c2f 100644
--- a/daemon/face/tcp-transport.cpp
+++ b/daemon/face/tcp-transport.cpp
@@ -31,8 +31,7 @@
 #include <sys/ioctl.h>
 #endif
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_MEMBER_INIT_SPECIALIZED(StreamTransport<boost::asio::ip::tcp>, TcpTransport);
 
@@ -192,5 +191,4 @@
   StreamTransport::doClose();
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face