Added marking queue, and made tutor clients callbacks.

Implemented persistent tutor client. ...

Hopefully this solves the weird issues we were seeing with the tutor
clients deadlocking.  Will also make the Android client simpler which
should again reduce race conditions.

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.

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