Light Hours for garden wrong when onTime < offTime

[docktordreh]

The calculation for displaying the amount of time the light is turned on for uses the absolute time between on and off. In cases where the lightsource is configured to be on during the night (e.g. light turns on at 22:00 and off at 16:00), this results in displaying the off-time as on-time. (6h, because |16-22|=6, yet in reality it's 16-22+24=18)

I wrote something fixing that earlier, I'll add that to the issue when I get to it.