- random value from the range
- derive(NothingBetween)
  Auto-implement NothingBetween when a Step exists.  Else returns false.
- MultiInterval + GIST index
- parsing and multiranges => should allow quotes bounds
- General/Algorithms/overlap_intervals.ads
- Boost interval_map to associate values with intervals
- use Either (https://docs.rs/either/latest/either/enum.Either.html) instead
  of Pair.
- Interval::translate()   to change both bounds.
- IntervalSet in no_std mode

- Multi: difference_set(IntervalSet<T>)
- Multi: symmetric_difference(MultiInterval<T>)
- Multi: strictly_right_of_interval
- Multi: splitting strategy