Exit application — Exit application after query
Closes all windows and exits the application.
If any open windows hold any form of “unsaved” data, the user will be queried whether to save that data or discard the “changes” or whether to cancel the exit operation.
If all windows could be closed successfully, the user will be queried whether she really wants to exit the application and depending on that the application will quit or stay open.
In case the application is allowed to quit, the current settings will be saved if configured to do that upon exit, and the program will finally close its main window and terminate the process.