Scheduling: Add filter for satellites in sunlight/shadow

Add a filter to the observations/new page to filter for satellites which are either both, at least partly in sunlight or shadow during a pass. This would improve the scheduling efficiency for satellites which are only active when illuminated.

Example use-case: https://community.libre.space/t/kraksat-satellite/4236/27

[KrakSat] is in sunlight on the Southern hemisphere. [..]

We need a tick box on the scheduling interface that will only schedule passes in sunlight or night time. The ephem library provides a function to tell whether a satellite is sunlit or not.

Related #536.