Adds logging level tag to log messages

src/core/include/Logger.hpp

@@ -23,9 +23,9 @@ class Logger {
 
     class Sink {
         private:
-        bool lineIsPrefixed;
-        Logger& parent;
-        const Logger::Level level;
+        bool lineIsPrefixed_;
+        Logger& parent_;
+        const Logger::Level level_;
         void prefixLine(bool resetToFalse = false);
         public:
         Sink(const Level level, Logger& parent);