fixed xml2json and json2xml scripts to support new WA output format.

[samimarreed]

WA has new output schema, which looks like this :

"output": {
            "generic": [
                {
                    "values": [
                        {
                            "text": "val1"
                        },
                        {
                            "text": "val2"
                        }
                    ],
                    "selection_policy": "random",
                    "response_type": "text"
                }
            ]
}        

this pull requests fixes the scripts ( xml2json and json2xml ) to support this change.