Surface time "days since landing" inaccurate when day length modded #85

Pretty much, when you use a mod like Clockwork that can modify the length of a game day, the days since landing option of the time sensor is inaccurate. Would be good to use surface.ticks_per_day vs a hard coded constant.

What might be even better, is to store surface.daytime to a global var, then each time you update the time, use this to check to see if the current surface.daytime has rolled over (updating the global var with the new time after) and increment another counter that you keep in global if it has.