Pretty-print the JSON in the config file

From James Hong at MathWorks Tech Support:

```matlab
uglyJson = jsonencode(struct('a',1:10,'b','hello'));
gson = com.google.gson.GsonBuilder;
gson = gson.setPrettyPrinting().create();
jp = com.google.gson.JsonParser;
je = jp.parse(uglyJson);
prettyJsonString = gson.toJson(je)
```