HPCC-9906 Support DATASET(n, transform, LOCAL)

Added localAttribute options, 'LOCAL' and 'NOLOCAL', to allow datasets to be created with n rows on each node and n rows on a single node respectively.

Signed-off-by: JamieNoss <james.noss@lexisnexis.com>
Merge pull request #5005 from jamienoss/issue9906-datset-local

HPCC-9906 Support DATASET(n, transform, LOCAL)

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>