HPCC-11593 Document ecl queries copy-set

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
HPCC-11593 Edits from code review

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
Merge pull request #6023 from JamesDeFabia/11593Document_ecl_queries_copy-set

HPCC-11593 Document ecl queries copy-set

Reviewed-By: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>