Move Jolog manager to a separate module

The jolog module was getting to be too large.  Moving the manager (and
soon other components) to a separate file should also help me keep the
components more independent too.
Refactor manager loop

The new code is cleaner (fewer nested indentation levels), faster
(uses index for handle_event/3) and more intuitive.

The change in intuition comes with the way we now switch between join
patterns and manager events.  This code processes as many join
patterns as possible then moves on to processing manager events.  We
continue processing manager events until a send_message/1 event
arrives.  As soon as a new message has arrived, it's possible for new
join patterns to succeed so we switch back to processing those
instead.

I predict that this will give us fewer context switches and should
improve performance.  Although, I'm not at the point where performance
matters yet, so that's just speculation.
Debug message when manager blocks

We don't want the manager to block very much.  We'd rather have her
performing useful work or taking care of the bookkeeping.