Refactor namings of serializers etc.

Source/MQTTnet/Protocol/MqttAuthenticateReasonCode.cs

@@ -0,0 +1,9 @@
+namespace MQTTnet.Protocol
+{
+    public enum MqttAuthenticateReasonCode
+    {
+        Success = 0,
+        ContinueAuthentication = 24,
+        ReAuthenticate = 25
+    }
+}