Included missing function (coscine/issues#461)

src/Logging/CoscineLogger.cs

@@ -223,6 +223,11 @@ namespace Coscine.Logging
             Log(messageType, context, null, exception);
         }
 
+        public void Log(LogType messageType, string message, Exception exception)
+        {
+            Log(messageType, null, message, exception);
+        }
+
         public void Log(LogType messageType, Type context, string message, Exception exception)
         {
             UpdateActiveLogs();