Add option to disable backlight

Add an option to disable the backlight on the Neostats at night or permanently.

We tend to get quite a few short power cuts/disturbances at night, which result in the Neostats lighting up the backlight when the power is restored, which wakes everyone up in their bedrooms … not a good situation.

If the backlight could be disabled this would be great or another option would be to not light the backlight when power cycled.

Perhaps this could be combined with another suggestion I saw on here that was asking if feature could be added where backlight could be used as a nightlight.