#880 customize loggers keep track of timestamp and have toString defined

[Jeremy Faden]

For years I've thought about having a subclass of Logger returned by LoggerManager, which would have a toString which identifies the logger and its setting, and would also keep a timestamp of the last log message, so that loggers could be sorted by message timestamps in the LoggerManager GUI.

[Jeremy Faden]

I don't expect this would affect performance.