Users should be warned when they are about to close a project with unsaved changes.

[jhs507]

When a user attempts to use the project->close, project->exit, project->open, or close the application while the currently loaded project is not saved they should be alerted to this fact and be given a chance to save.

Requested in user assessment #365

[jhs507]

The GUI object can store a variable that indicates if the loaded project has been altered since being loaded.

[jhs507]

The project altered field is now updated when the user takes actions that change the project state f828fb7

[jhs507]

Reopened because the case of closing the window with the X is not covered.

[jhs507]

Closed with fd2a8fc