HPCC-8799 WsEcl support for JSON via HTTP-GET and FORM-ENCODED-POST

An HTTP-GET or application/x-www-form-urlencoded POST to a URL
of the format: "/WsEcl/submit/query/<target>/<queryid>/json" will
return a JSON formatted response.

For HTTP-GET stored paramter values can be passed as URL parameters:

/WsEcl/submit/query/<target>/<queryid>/json?stored1=abc&stored2=33

Signed-off-by: Anthony Fishbeck <Anthony.Fishbeck@lexisnexis.com>