Should JsonObjectStream expose a reference to JsonBuffer?

[tius2000]

To create an array of array the method JsonBuffer::createArray() is required:

DynamicJsonBuffer buffer;
JsonArray& list = buffer.createArray();
JsonArray& item = buffer.createArray();
item.add(1);
list.add( item );

However, the class JsonObjectStream does not a reference to the underlying JsonBuffer. If this is desired, I will provide a patch.