Integrate LunarSky module to do sensitivy predictions for array on the moon

[steven-murray]

This uses @aelanman's LunarSky. @jpober suggests this.

[jpober]

This might be as simple as switching _utils line 140 to a MoonLocation object provided by lunarsky. I will test at some point!

[jpober]

Looks like we also need to change line 226 in observatory.py to update obs_duration for lunar days (as opposed to earth days). That will likely also cause other consistency checks to fail (e.g. line 94 in observation.py that insists obs_duration be less than 24 hours)

[steven-murray]

That makes sense. We could generalize that easily.