Expose _upload_folder_recursive and add authentication token as parameter

[sankhesh]

Currently the method pydas.api._upload_folder_recursive is not exposed.

Secondly, it relies on the current session communicator. If one logs in using the api_key, this method fails as it does not have a reference to the current session.

[cpatrick]

@sankhesh Could you report this on https://github.com/midasplatform/pydas instead?