Feature: domains

New module domains implements classes to represent parameter domains.

Main features are

• in-testing
• next_[largest,smallest,closest] methods that return numbers from the domain next largest/smallest/closest to a test value
• & composition, which returns a domain that is least inclusive out of the two operands (similar to set.intersection)

Could also imagine | composition (similar to set.union).

Implemented so far are

• DiscreteInterval: basically like range(start, stop).
• ContinuousInterval: same except not limited to ints.
• ReciprocalDiscreteInterval: a floating numerator divided by a discrete interval.
• BoundedSet: Subclass of frozenset with bounds.