HPCC-9874 Improve WsEcl JSON formatting for xml types used by ECL

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Merge pull request #4752 from afishbeck/jsonUnsignedx

HPCC-9874 Improve WsEcl JSON formatting for xml types used by ECL

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>