BatchUploader: special treatment for Oracle

• When using the callback_url argument of robotupload, if the server that is going to handle the feedback does not directly understand the POST request with an application/json mimetype, as is the case of Oracle application, it is now possible to further specify the argument special_treatment=oracle, in order to have the POST request further encoded in application/x-www-form-urlencoded with a single form key called "results", containing the original JSON content.