private void setGenerator(JsonGenerator generator, FieldConsumerSettings settings) {
        this.generator = generator;
        this.fieldConsumer = generator == null ? null : createFieldConsumer(generator, settings);
    }
Adds JSONP (Json with padding) support.

Basically, if the JSON renderer receives a query parameter "jsoncallback=...",
the JSON response will be wrapped in a function call with the name specified
by the client. This side-steps the same-origin policy, thus supports calling
Vespa from javascript loaded from a different domain then the Vespa instance.
container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java