Log correct row number with header consistency check

[jeffkole]

In Phase#check_headers_consistent since the context.current_row is not updated when the warnings are logged, all of the warnings are associated with the last row number, even though the full row (along with its row number) are passed into the add_warning function call.

check_headers_consistent should log which row the error occurred on.

[jeffkole]

Need to revalidate this issue, as it may have been fixed with recent changes.