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/fw/self-learning-strategy.hpp b/daemon/fw/self-learning-strategy.hpp
index 47e59af..118fe3d 100644
--- a/daemon/fw/self-learning-strategy.hpp
+++ b/daemon/fw/self-learning-strategy.hpp
@@ -30,8 +30,7 @@
 
 #include <ndn-cxx/lp/prefix-announcement-header.hpp>
 
-namespace nfd {
-namespace fw {
+namespace nfd::fw {
 
 /** \brief Self-learning forwarding strategy
  *
@@ -138,7 +137,6 @@
   renewRoute(const Name& name, FaceId inFaceId, time::milliseconds maxLifetime);
 };
 
-} // namespace fw
-} // namespace nfd
+} // namespace nfd::fw
 
 #endif // NFD_DAEMON_FW_SELF_LEARNING_STRATEGY_HPP