HPCC-11464 Default string stored definitions to variable length

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5907 from ghalliday/issue11464

HPCC-11464 Default string stored definitions to variable length

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>