Added marking queue, and made tutor clients callbacks.

Code cleanup. Been playing with a few different static code analysis ...

tools.  Used them to recommend the changes made in this commit.

Added a stress test for the BroadcastResponder.

Clean up. Fixed logging statements, added private constructors to ...

classes that should never be instantiated.  Fixed author names to be
consistent.

Tweaked tests a bit. StressTest now loops.

Changed to mousePressed rather than mouseClicked because clicking labels is a ...

bit weird (seem less tolerant of movement during click than buttons).

Also attempting to fix problem with tutor client occasionally losing sync which
is probably due to threading (maybe server request thread deadlocking).

Added some additional testing classes.

Whole bunch of stuff: ...

- Refactored the map panels to separate the queue label into its own panel.
 - Made queue label overflow without resizing the panels that contain it.
 - Fixed some threading issues by making expanding a couple of synchronized blocks into full method syncs.
 - Added some more constants for things (version number, exit codes).
 - Show message dialog when the server can't be found.
 - Added a test class that causes a message flood for testing threading and queue overflow.

Added a simple test that simulates all users in a lab requesting help at ...

once.  Tests how the UI responds to overflow in the queue label, and the
general responsiveness and reliability of the system.