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/unix-stream-transport.cpp b/daemon/face/unix-stream-transport.cpp
index a051ca9..76652f3 100644
--- a/daemon/face/unix-stream-transport.cpp
+++ b/daemon/face/unix-stream-transport.cpp
@@ -25,8 +25,7 @@
 
 #include "unix-stream-transport.hpp"
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_MEMBER_INIT_SPECIALIZED(StreamTransport<boost::asio::local::stream_protocol>, UnixStreamTransport);
 
@@ -48,5 +47,4 @@
   NFD_LOG_FACE_DEBUG("Creating transport");
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face