Managing parameter input

[kination]

Currently, it needs to generate json -> string for POST:

Indexes book = ms.getIndex("books");
        
JsonArray jsonArray = new JsonArray();
JsonObject jsonObject = new JsonObject();
jsonObject.addProperty("1111", "alice in wonderland");
jsonArray.add(jsonObject);

// add new document "[{"1111": "alice in wonderland"}]"
String response = book.addDocument(jsonObject.toString());

To make this simple:

1. Accept JSON modules(Gson, Jackson, ...) as input
2. Create custom input format(it will use JSON module internally to convert input into JSON format)

[curquiza]

Closed by #36