CXX-265 Configure logging through startup options

A few comments/questions:

-For cleanup of appenders, there's a clearAppenders() function, and this will actually delete the appenders.  Though it seems clear that when you attach the appender you hand ownership of it over to the log domain, users using these options won't see that call, and I wonder if they'd be surprised by this behavior.  Also, since we're not using the appender handles at all, or allowing the user to use them, I wasn't sure how important it was to call clearAppenders() at all.

-Where should configureLoggingOptions() live?  Options.cpp seems like an ok option, but I think there's probably a better fit.  If I add a cleanup function that should probably live in the same place.

-Should there be a way to configure, through options, specific minimum logged severity levels for different logging domains?  If you were doing it manually, you'd be able to set it by component.
I chatted with Andy about this. He has two recommendations:
- Only permit one appender to be added
- Configure the Options structure to take a pointer to a user provided factory function that creates the appender subclass they want to use.

That way, we force the user to construct an appender which we then own, and we can sidestep the auto_ptr gotchas.

I think it is a reasonable suggestion, but lets go over it in person when you have a few minutes.