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/asf-strategy.hpp b/daemon/fw/asf-strategy.hpp
index 95d1d71..0e6f3a2 100644
--- a/daemon/fw/asf-strategy.hpp
+++ b/daemon/fw/asf-strategy.hpp
@@ -31,8 +31,7 @@
 #include "asf-probing-module.hpp"
 #include "retx-suppression-exponential.hpp"
 
-namespace nfd {
-namespace fw {
+namespace nfd::fw {
 namespace asf {
 
 /** \brief Adaptive SRTT-based Forwarding Strategy
@@ -97,7 +96,6 @@
 
 using asf::AsfStrategy;
 
-} // namespace fw
-} // namespace nfd
+} // namespace nfd::fw
 
 #endif // NFD_DAEMON_FW_ASF_STRATEGY_HPP