SI-6736 Range.contains is wrong

Removed once-used private method that was calculating ranges in error and corrected the contains method (plus improved performance).
Reasonable Range operations consistently work when overfull.

Operations are reasonable when they don't require indexing or conversion into a collection.  These include head, tail, init, last, drop, take, dropWhile, takeWhile, dropRight, takeRight, span.

Tests added also to verify the new behavior.