Add logging framework.

DEBUG messages are completely optimized out if NDEBUG is defined.

src/ntcore_cpp.cpp

@@ -13,6 +13,7 @@
 #include <fstream>
 
 #include "Dispatcher.h"
+#include "Log.h"
 #include "Storage.h"
 
 namespace nt {
@@ -173,4 +174,10 @@ const char* LoadPersistent(
   return nullptr;
 }
 
+void SetLogger(LogFunc func, unsigned int min_level) {
+  Logger& logger = Logger::GetInstance();
+  logger.SetLogger(func);
+  logger.set_min_level(min_level);
+}
+
 }  // namespace nt