Major Description
When the client cares about getting results in sorted order, the BatchScanner, as nice as it is, is mostly irrelevant.
One interesting property of the Scanner is that it will begin to pre-fetch more results after the 3rd batch of results has been fetched from the server.
Clients may have an idea of the number of records that will be returned by a scan, and thus will have an idea about how they want to control such a readahead. It would be nice to allow the client to control after how many batches the readahead thread starts.