Export/Download methods to return extra data

[countnazgul]

At the moment export/download methods are returning the raw data. This should be changed so the raw data to be returned under the file property and other extra information to be returned under additional properties.

For example app.export to return:

{
  "file": "Binary-data-here",
  "name": "qlik-app-name.qvf",
  "id": "123-123-123-123"
}

[countnazgul]

closed with 749f953