Add stream support to Scanners

[keith-turner]

It would be really nice if the fluo scanners had methods to return java streams.

[mikewalch]

It looks like what is needed for this issue is a stream() method should be added to CellScanner, ColumnScanner, RowScanner like below:

public interface RowScanner extends Iterable<ColumnScanner> {

  default Stream<ColumnScanner> stream() {
    return StreamSupport.stream(spliterator(), false);
  }

  default Stream<ColumnScanner> parallelStream() {
    return StreamSupport.stream(spliterator(), true);
  }
}

For more information on streams, check out this stackoverflow question and this tutorial