HPCC-10949 DOCS: document Spray Variable and Spray BLOB

FIX HPCC-10949 DOCS: document Spray Variable and Spary BLOB
Added language to DH-Man module to cover both Variable and Blob.
Blob issue # HPCC-10948

Signed-off-by: g-pan <greg.panagiotatos@lexisnexis.com>
Merge pull request #6371 from g-pan/H10948-ECLWaSpry

HPCC-10949 DOCS: document Spray Variable and Spray BLOB

Reviewed-By: Jim DeFabia <james.defabia@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>