HPCC-11006 Download zipped WU XML if it is big

In this fix, the size of WU XML is returned in WsWorkunits/WUInfo
response. WUInfo xslt page checks the size. If the size is greater
than 5MB, the page displays a Download XML link. When the link is
clicked, the WU XML is zipped and downloaded.

Signed-off-by: Kevin Wang kevin.wang@lexisnexis.com