HPCC-10895 Document "allow-foreign" option in CLI

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
HPCC-10895 Edits from review feedback

Signed-off-by: JamesDeFabia <James.Defabia@LexisNexis.com>
Merge pull request #5478 from JamesDeFabia/10895_document_CLI_Options_ForeignFiles

HPCC-10895 Document "allow-foreign" option in CLI

Reviewed-By: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>