HPCC-9900 DFUPlus does not support escape option for CSV spray

Add missing code and extend usage info.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #4766 from AttilaVamos/HPCC-9900-fix

HPCC-9900 DFUPlus does not support escape option for CSV spray

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>