[logback-dev] Better introspection into logging setup

[Durchholz, Joachim]

> Perhaps you are talking about an extension to the 
> jul-to-slf4j bridge?

Yes, that's what it all boils down to.

> That would not entail any change to the 
> real slf4j api.

Well, how would it know what loggers to configure?

... hmm, I now see that this should be a solved problem. (That's what
you get for too much black-box thinking: I didn't look into what's going
on inside the *-over-slf4j jars.)

A quick source scan through jcl-over-slf4j revealed that the code goes
through some hoops but I should be able to rip it off for jul-to-slf4j
with little effort.
What I didn't see right throught he first scan is where the
configuration for the jcl loggers come from. Is it logback.xml, or is it
whatever configuration is present for jcl? (logback.xml would be sweet.
Things are easier to manage if I don't have to keep notes what
subproject uses what logging machinery.)

Regards,
Jo