Add minimum culmination in station fields

Add minimum culmination in station fields and use it on calculating passes.

Minimum culmination will be the minimum maximum elevation of a pass that station owner would like to be scheduled in its station. Not to be confused with min horizon, which is the elevation in degrees that an observation starts from and ends to.

Example: min horizon: 2 degrees min culmination: 10 degress

Calculated passes: All that have maximum elevation at least 10 degrees and their start and end will be at 2 degrees.