Toggle Absolue/Relative
Ehh, when we're displaying time, relative is ETE, while absolute tries to give ETA, but I haven't been able to get the right local timezone offset on the empeg. It looks like it picks UTC + double the actual timezone offset as localtime, not sure why.

When displaying distances to waypoints, it doesn't make any difference for the next waypoint or the final destination, but it matters for the ones after the next, it should be obvious when you have a route loaded and are in the text display.

For a lot of these options I'm assuming that they'll just at some point get obsoleted or fixed to some default value. Possibly read from config.ini. I really don't want to add anything that writes to the disk unless absolutely 100% necessary. Another advantage of that is that it should be virtually impossible to get into a wedged state that isn't recoverable by simply pulling the plug and rebooting.