Consider adding support for Array.sortWith

[adam-wyluda]

The implementation could be based on util.Sorting.quickSort.

I'm not sure if we should also support sortBy function, since it would require client to provide a reference to an on-heap implementation of Ordering typeclass. Perhaps our interface of sortWith (or we could name it just as "sort" in that case) could take additional mapping argument with identity function as a default value.