'only_single_header_row' that turns the output into CSV format.
In that mode all meta data is skipped except for a single header line
with the fields names. Example:
local my_filter: Log::Filter = [$name = "my-filter", $writer = Log::WRITER_ASCII, $config = table(["only_single_header_row"] = "T")];
Contributed by Carsten Langer.
