PPageMisc: Display a message in case no customized keys are present.
PPageMisc: Change filename for export keys.
MPC: Delete settings export registry file in case of failure.
MPC: Export settings now takes a path instead of displaying a save dialog.
DSUtil: ExportRegistryKey now sets GetLastError().
Add the ability to choose the scale factor for the auto-fit zoom.

The factor is relative to the screen size.