Test horizon constraints for entire time duration

[wtgee]

It's not clear from basic example if horizon is only checked for initial time slot or for the duration the target is above horizon.

[jermainegug]

Anything that we could add to the example to check this?

[wtgee]

I wouldn't quite start on this yet as I need to do some checking on the other constraints to make sure it is even working consistently. We are having problems with the Duration constraint not properly accounting for the meridian (#361) and I think it is somewhat related.