HPCC-9970 Default persist files to expiring after 14 days

Can be configured with expirePersists and defaultPersistExpiry debug options

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4889 from ghalliday/issue9970

HPCC-9970 Default persist files to expiring after 14 days

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>