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/tools/ndn-autoconfig/procedure.cpp b/tools/ndn-autoconfig/procedure.cpp
index cda39ad..f7295d3 100644
--- a/tools/ndn-autoconfig/procedure.cpp
+++ b/tools/ndn-autoconfig/procedure.cpp
@@ -29,9 +29,7 @@
 #include "multicast-discovery.hpp"
 #include "ndn-fch-discovery.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 using nfd::ControlParameters;
 using nfd::ControlResponse;
@@ -138,6 +136,4 @@
     });
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig