Convert current ddf test data to json

[gerrycampion]

We can do this in bulk using a single script.

[ASL-rmarshall]

We think there are different requirements for Excel and JSON test data. We'd want JSON test data to include a full study definition, so there probably wouldn't be enough information in the existing Excel test data files to create full JSON test data.

This is just part of the (eventual) effort in converting existing tabular rules to JSONata rules.