Consider allowing generation of .bonsai workflow artifacts

[bruno-f-cruz]

If we are moving with the adoption of custom json tags as suggested in #40, it would be interesting to allow the generation of full workflows as part of the generation of a given object. This could be initially afforded by simply adding the raw xml string to the operator. This would allow users to generate a json-derived spec with its own implemented .bonsai operators.

An extension of this idea would be to allow csharp snippets to also be added in line when the generated classes are written.