Sunrise and -set must recomputed if one of the following conditions is met:
* The date changed (based on the selected timezone)
* Location (Lat/Lon) changed
* Sunset type changed
So instead of calculating that every minute just do it on update via web interface or date change.
If a new config is uploaded, the DTU gets restarted. There is no need to initiate a recalculation in this case.
