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).

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.

Lots of improvements: ...

- Separated the queue label into a new panel.
  - Got rid of the now unnecessary AbstractMap base panel for maps.
  - Made the queue label handle overflow (put it in a scroll pane)
  - Show a message dialog for when now map can be found
  - Machine IDs can now be passed as command line arguments - this
    overrides the COMPUTERNAME env var.
  - Made the request/cancel methods synchronized instead of using a sync
    block inside those methods.  This seems to have improved the overall
reliability when mass requests are made, and hopefully fixes the
deadlock that the tutor-client occasionally had.

Improved TutorClient. Huge refactor. Icon now read from classpath/jar.