Allow OAuth1 callback to specify query string parameters

They are then parsed and provided to underlying HTTP package. We have to parse them so that signing of requests works properly. In addition, nonce used in the request is stored in the response so that user can verify JWT payloads returned from the server.
On the other hand, any error message from the server is in response.content. It is quite useful for debugging. (So maybe we should display response.content if nor tokens.oauth_token nor tokens.oauth_token is available.)