InternalLogger writes to output even if logging is disabled in configuration

[LukasNeoproud]

I would like to make MetroLog completely silent if an application is built in release configuration. First I disabled logging in configuration LogManagerFactory.DefaultConfiguration.IsEnabled = false; but MetroLog still wrote messages like this: Created Logger 'App'.

I later found out that InternalLogger class is responsible for this output. However, it is enabled for all log levels and cannot be disabled in any way. I suggest to add IsEnabled property to InternalLogger. I am willing to make a pull request with this change but I am not sure if it is the right solution for this problem.