Logging tweaks [1628]

This pull request contains the changes discussed at the recent logging meeting.

Currently implemented:

* Look for a "local" `logback.xml`, *outside* of the McV repo, and if the specified `logback.xml` does not exist, McV will fall back to the `logback.xml` located in the root of `mcidasv.jar`.

* mcidasv.log will now be rolled upon starting McV, and the rolled logs will be moved to `$USERPATH/logs/mcidasv_yyyyMMdd_HHmmss.log`.

* Logger calls from VisAD's `AddeServerInfo`, `AddeTextReader`, and `DataSetInfo` have been disabled in the default `logback.xml`.

Not Yet Implemented:

* Still not sure about removing the "preamble" from the *only* the Jython logging.
  1. Haven't had much luck with getting two inputs into `mcidasv.log`. 
  1. I did a little experiment and just edited an existing log file to remove the Jython preamble…and the result was pretty hard to read. I'd rather go back to sticking things into a `jython.log` file.