HPCC-10949 DOCS: document Spray Variable and Spray BLOB

FIX HPCC-10949 DOCS: document Spray Variable and Spray 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>

@JamesDeFabia please review
@g-pan Are you planning to address this before I pull? It's not a new issue...