fields, auth_response, session restore, init with dict

- fields can be selected in api path using for example "me?fields=id"
- create a function for get the current user auth_response
- now login function returns a callback response with user auth_response that
contains access_token, user_id, expires_in. Similar to FB api
- login function stores the auth_response in the session
- for scal. issues, init function receives a dictionary instead of a list. Similar to FB api
- new argument in init function for restore sessions with auth responses

These branches can be automatically merged.
Ty.