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.

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.