Tim Johnson

### Description Extend the scope of the JSON schema to include validation of the relationships section of the profile (which is described [here](https://github.com/finos/datahelix/blob/master/docs/RelationalData.md)). ### Changes - Add relationships section to...

### Changes Update from: 2018 - 2019 to: 2018 - 2020.

The datahelix-ui project was created in order to develop a front end for DataHelix, but this software didn't end up get used, it was superseded by the current online playground....

The playground was down and we didn't know (#1693). Can we add some tests to detect future issues? - If DataHelix changes then make sure the playground isn't broken (just...