HPCC-3060 Add fileview2 support for JSON format workunit results

Also integrate fileview2 JSON support into WsEcl to common up JSON
result formatting and improve performance.

Also add JSON result format to /WsWorkunits/WUResult.json

Also fix JSON set item formatting, and improve formatting for "ALL"
in a Set.

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>