Move transformation functions to jskos-tools

The transformation functions such as [csv-to-concept](https://github.com/gbv/jskos-cli/blob/main/lib/csv-to-concept.js#L18) should better be moved to [jskos-tools](https://github.com/gbv/jskos-tools) to directly be used as library in web application.

See https://github.com/gbv/jskos-tools/issues/34