Calculate RiseTransitSet based on timezone

[onekiloparsec]

Calculate RiseTransitSet based on timezone

[andris-zalitis]

One option would be to remove:
let midnight = self.celestialBody.julianDay.midnight and just use JulianDate itself, but then we would loose the ability of running code that asks for moonrise/moonset for a local time with hours and minutes, without caring to convert it to local midnight.

Therefore I have opted to use localMidnight(timeZone:) to solve this. Note that although we already have localMidnight(longitude:) it does not fully solve the problem because there are differences between midnight calculated based on longitude vs midnight calculated based on time zone.

[andris-zalitis]

BTW I've used moonrise/moonset in the example because those change more rapidly from day to day than sunrise/sunset or dawn/dusk.

[onekiloparsec]

This is great again, thanks for checking this in details! Again, once we settle the discussion about midnight in #54, I'll happy to merge that work.

[onekiloparsec]

Quick note: this isn't settled yet, but I'm still on it. I have tracked down (and down and down...) the problem of rise transit and set times. And it seems, somehow, I don't get right the equatorial coordinates for the date. I'll be in vacations for some time, but I'll be back!

[onekiloparsec]

I found the root cause of our problems. I was computing equatorial coordinates of solar system objects based on ecliptic coordinates. But not "normal" (geocentric) ecliptic coordinates, rather the heliocentric ones! I didn't know those latter coords existed anyway.

I had to change a bit the CelestialBody protocol, and I managed to make all tests pass. However, some of them with an accuracy that is not satisfactory. I can't do more for now, as I am leaving for a few vacations. But I am relieved this important issue is solved.