Minor functions update

- Added parameter and return type setting to all functions to make it clearer what each function can return.
- Changed default settings to allow auto-save with an interval of 15 seconds.
- Cleaned up code for `quitApp` function.
- When an error shows up, you can cancel it and try again.
- Removed unused function.
- Changed where the program looks for the settings file. (this will help when moving the program between different computers)
- Closed #66

Note: Will probably upgrade from *Python 3.8* to *Python 3.10* some time soon.