HPCC-8181 Add ecl packagemap validate to docs

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
HPCC-8181 Added more info on ecl packagemap validate from code review

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
Merge pull request #4108 from JamesDeFabia/ecl_packagemap_validate_HPCC-8181

Ecl packagemap validate hpcc 8181

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>