Refactor to clarify use of "read_column_names" vs. "use_column_names".
Refactor to clarify use of "read_column_names" vs. "use_column_names".

This also allows for future support for XML, JSON, and Bash modes where we
read and ignore the first CSV row but don't use column names in the output.

archiecobbs/csvprintf,archiecobbs/csvprintf