Added overlay to modify grades instead of JOptionPane.
Added right click option to add new grades for an assignment in the gradebook.
Now stores code sorting method.
Will not close until background thread has completed.
	Shows a popup window giving you the option to cancel closing until background thread finishes.
Will now prompt to close if an application is running.
Refactored BackgroundThread
	Slight possibility of some bugs because of it.
Now stores window position and size between sessions.