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/lp-reassembler.hpp b/daemon/face/lp-reassembler.hpp
index 59db89b..8009c67 100644
--- a/daemon/face/lp-reassembler.hpp
+++ b/daemon/face/lp-reassembler.hpp
@@ -30,8 +30,7 @@
 
 #include <ndn-cxx/lp/packet.hpp>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 /**
  * \brief Reassembles fragmented network-layer packets
@@ -149,7 +148,6 @@
   return m_partialPackets.size();
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_LP_REASSEMBLER_HPP