Next steps on logging documentation

[jcfreeman2]

There's lots of good stuff already available between the README.md and the Wiki pages. A couple of quick thoughts:

• Some of the material is clearly meant for developers and/or is obsolete (e.g., the Feb-26 notes on how to set up daq-buildtools so you can build logging, or notes on how to update from ers to logging messages). That should get cut out.
• Would a very basic example program be helpful? E.g., one which prints TLOG_DEBUG(TLVL_TURN_ON_DEBUG_MESSAGES) << "This is a debug message" where users of the logging package could then play around with turning the message on and off, etc.?