[FR]: Auto database exporting

[RetroAbstract]

Brief description of the feature request

This feature would allow the user to automatically export their database and/or settings automatically with the addition of a "Automatically export every: X days, X hours, X minutes and X seconds" option in the already existing "Backup database/settings" window (File > Backup settings).

RSS Guard would auto-export Database & Settings depending on whether or not the Database box and Settings box are ticked.

RSS Guard would also remember the selected output directory where the database/settings are exported to.