Add internallogger event(s)

[304NotModified]

Easier to subscribe than InternalLogger.LogWriter

[snakefoot]

Would make sense to have a delegate. Maybe with these parameters:

Logger(Type contextType, string contextInfo, LogLevel level, string message, object[] parameters)

• Type contextType would be Target.GetType().
• string contextInfo could be File(Name=myfile)

This would allow one to setup a listener for all errors from DatabaseTarget, by filtering on the contextType.

Maybe need some special logic so a Layout that belongs to a certain target is able to signal that it comes from a certain contextType / contextInfo.

[snakefoot]

Resolved with #3796