feature/file_upload_additional_params

There is a requirement in a story where we need to send some additional details along with the files to the server side during file upload, so added a property <code>formData</code>, fileUpload widget uses this property to send to server as per the official documentation [details](https://github.com/blueimp/jQuery-File-Upload/wiki/How-to-submit-additional-Form-Data#adding-additional-form-data-programmatically)