Add convenience methods to controller specs to work with JSON

[ipolevoy]

Example posting JSON as an object:

Map requestDoc = ...
request().json(requestDoc).post("create"); 

JSONMap response = responseContentMap();

...
JSONList response = responseContentList();

[ipolevoy]

Added in controllers:

@POST
    public void index1(){
        JSONMap request = .....
        respondJSON(request);
    }

The method respondJSON() also sets the Content-Type=application/json

---

Controller Specs:

Sending requests:

request().json(obj).post("index1"); 

will convert the obj to a JSON format (String, Map, List, Object). Will also set Content-Type=application/json automatically

Parsing controller output:

JSONList responseList = responseJSONList();
JSONMap responseMap = responseJSONMap();