Add Interval implementation

Add an Interval implementation like:

data class Interval(val from: Instant, val to: Instant)

[imanushin]

I think think class can be extended:

data class Interval(override val start: Instant, override val endInclusive: Instant): ClosedRange<Instant> {
      init {
           require(start <= endInclusive) {
                 "Start should be before end, actual data: $this
           }
      }
}

Also I think we can also support sequences generation via implementing feature like this.

[Whathecode]

Update: I now included and published InstantInterval on Maven as part of the Whathecode/kotlinx-interval library.