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).

Stupid NetBeans random project file changes.

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

Initial commit.