Build examples for containers by referencing unit tests #68

#66 has the inverse logic - where building blocks are being used to decompose complex objects where examples exist for the complete schema.

But when constructing a complex schema you may want to unit test or profile components then collate them.

Could we support a $ref or similar in JSON files and have an inbuilt transformer whose job is to dereference these and construct the validatable container from referenced parts?

The only downside here would be potentially needing chainable transformers - or pre- and post- transformers.

We probably want "transform to" capability anyway - so is this just a form of that?