Listing to json conversion

I think this is ready to go now.
 - agreed with Tony R which security questions need to be converted to 'choose as many as apply' fields instead of 'choose one'
 - Dates now in standard format for validation at the API
 - Updated version number for post-switch-off releases
Actually, I just checked and the database has `bigint` as the data type for supplier ID. The SSP should probably have used a numeric type for supplierId rather than a String, but it was pulling the ID from the cookie as a String and not converting to an int.

So I think using a numeric type here is better as it will fit in with the marketplace DB schema.