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/rib/readvertise/host-to-gateway-readvertise-policy.cpp b/daemon/rib/readvertise/host-to-gateway-readvertise-policy.cpp
index 5aa6e3b..2d8d3a5 100644
--- a/daemon/rib/readvertise/host-to-gateway-readvertise-policy.cpp
+++ b/daemon/rib/readvertise/host-to-gateway-readvertise-policy.cpp
@@ -30,8 +30,7 @@
 #include <ndn-cxx/security/pib/identity.hpp>
 #include <ndn-cxx/security/signing-helpers.hpp>
 
-namespace nfd {
-namespace rib {
+namespace nfd::rib {
 
 const name::Component IGNORE_COMPONENT("nrd");
 const time::seconds DEFAULT_REFRESH_INTERVAL = 25_s;
@@ -85,5 +84,4 @@
   return m_refreshInterval;
 }
 
-} // namespace rib
-} // namespace nfd
+} // namespace nfd::rib