HPCC-12470 Document IMPORT ^ syntax

Signed-off-by: Jim DeFabia <jamesdefabia@lexisnexis.com>
HPCC-12470 Edits based upon review

Signed-off-by: Jim DeFabia <jamesdefabia@lexisnexis.com>
Merge pull request #6594 from JamesDeFabia/12470DocsImportCaret

HPCC-12470 Document IMPORT ^ syntax

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>