Restore plugged volume

The ability to restore unplugged volume is great, but it would make hearing-saver a lot easier to configure if you could also restore the plugged volume. That way, you just adjust your volume and when you plug/unplug hearing-saver automatically saves your volume for when you unplug/plug.

This also resolves issues where the volume sliders in the app don't behave the same as the volume sliders in the system menu (especially what point is vibrate and what point is low volume).