Nested json to datatable

This change allows nested json objects such as below to be converted to datatables containing datatables as column values. Currently nested datatables can be converted to nested json objects, this can convert that format back again.

```
[
  {
    "foo": "bar",
    "baz": [
      {
        "nestedfoo": "bar",
        "nestedbaz": "2",
      }
    ]
  }
]
```