Return a JSON Array for List Return Types

[jocrau]

A root operation that returns a list returns a JSON array as result. For example, the definition

type Query {
  machines: [Machine]
}

should have an example response like

{
  "data": {
    "machines": [
      { "machineId":  1234 }
    ]
  }
}

but currently generates

{
  "data": {
    "machines": {
      "machineId":  1234
    }
  }
}

This PR fixes this, by checking whether the return type is a list. It also accounts for non-nullable values.

[newhouse]

Thanks! I may change this around a little but, but looks good

[newhouse]

Published in 1.1.3