Make SDT output in JSON format

[tobbee]

The SDT output is currently not in JSON format but in plain text format. Should be changed to JSON.

[Wkkkkk]

Now we are printing SDT info as

{
  "SDT": [
    {
      "serviceId": 1,
      "descriptors": [
        {
          "serviceName": "ts-info",
          "providerName": "Eyevinn Technology"
        }
      ]
    }
  ]
}