Add ETL Test Generator

[jpreese]

This issue is part of an overall initiative to complete #195.

The documentation on how to add generators can be found here. If you get stuck or have any questions about adding this generator, please do not hesitate to reach out!

[hymccord]

I've started on this one.

[hymccord]

I've run into a design decision. The input from the canonical-data is of type IDictionary<int,IList<string>> which switches to default: in the ValueFormatter class. Would it be helpful to add this to the ValueFormatter class or do I just write some methods in the generator class that formats it for me while Arranging?

If wanted in ValueFormatter I think I will also need to add a FormatMultilineEnumerable method that doesn't output a variable name like the current one.

[ErikSchierboom]

@inkahootz Well, good point. It may be easier to just do the formatting in the generator class itself. We can always refactor to another method if needed later.

[ErikSchierboom]

Closed by #462.