HPCC-8953	Add roxie support for JSON/HTTP queries

New feature allowing native support for JSON queries in roxie.

Signed-off-by: Anthony Fishbeck <Anthony.Fishbeck@lexisnexis.com>
Merge pull request #4172 from afishbeck/json_roxie8953

HPCC-8953	Add roxie support for JSON/HTTP queries

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>