HPCC-9961 Expose contents of @kind DFU attribute in WsDFU/DFUInfo

It is requested that WsDFU should expose contents of @kind DFU attribute
as new field ContentType. This fix exposes the contents of @kind DFU
attribute.
Merge pull request #4813 from wangkx/h9961

HPCC-9961 Expose contents of @kind DFU attribute in WsDFU/DFUInfo

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>