[ADAM-511] Provide Ordering for ReferenceRegion

As covered in issue #511, ReferenceRegion shouldn't extend Ordered, but
rather should be ordered by an Ordering value which can be imported
implicitly.  This will fix some "diverging implicit expansion" errors,
and bring us more in line with the Scala documentation on Ordered (which
is intended to be used in classes that have "a single, natural ordering"
-- a description that doesn't apply to ReferenceRegion).

This commit makes these changes, with the new Ordering provided
implicitly in ReferenceRegionContext.  It also includes corresponding
changes to the ReferenceRegionWithOrientation handling, and (finally)
includes changes to downstream classes that use(d) the Region.compareTo
method.
Implementing the windowCounts method

added an empty test suite.