Improve pylvarray test coverage with pure C++ tests.

[corbett5]

We can improve the pylvarray test coverage with pure C++ tests as follows

template< typename T >
void testSortedArray()
{
  SortedArray< T > set;
  populate( set);
  SortedArray< T > copy( arr );
  PyObjectRef<> pySet = create( arr );
  mutate( pySet, copy );
  check( copy, arr, pySet);
}