Added marking queue, and made tutor clients callbacks.

Added map for CO3.18.

Removed private project properties from repository.

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

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

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.

Stupid NetBeans random project file changes.

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

Reworked threads, shutdown hook, and exit process to ensure requests are cancelled if student logs/out without cancelling manually.

Initial commit.