CSV headers / No headers selection on the CSV Parser Form

Currently CSV parser form displays this selection:

No headers

• Check if the imported CSV file does not start with a header row. If checked, mapping sources must be named '0', '1', '2' etc.

and it does not make sense. It's good to have this on the CsvParserFeedForm but here, on per feed basis the mapping can not change and thus the selection can only be harmful if user chooses the wrong option.

So instead of this element I suggest that we replace it with a read-only display of current mapped headers.