Restore to factory settings

I had an incident where ShotCut stopped outputting sound to the system speaker, though the Audio Loudness meter showed sound. After deleting the reg key with regedit the ability to output sound returned.

Unfortunately I didn’t save the reg key before deleting it, so I won’t be able to track down what may have happened unless it happens again. So my suggestion is to have a “Restore to factory settings” function which deletes the reg key, the settings folders and restarts ShotCut, so people can easily get a fresh start until we track down all bugs like the one I mentioned above.

This already exists in the Windows installer.