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/best-route-strategy.hpp b/daemon/fw/best-route-strategy.hpp
index 5b4e27d..484ac51 100644
--- a/daemon/fw/best-route-strategy.hpp
+++ b/daemon/fw/best-route-strategy.hpp
@@ -30,8 +30,7 @@
 #include "process-nack-traits.hpp"
 #include "retx-suppression-exponential.hpp"
 
-namespace nfd {
-namespace fw {
+namespace nfd::fw {
 
 /** \brief Best Route strategy
  *
@@ -75,7 +74,6 @@
   friend ProcessNackTraits<BestRouteStrategy>;
 };
 
-} // namespace fw
-} // namespace nfd
+} // namespace nfd::fw
 
 #endif // NFD_DAEMON_FW_BEST_ROUTE_STRATEGY_HPP