[repoapi] add an anonymous_cnx function
This function return an anonymous ClientConnection. It aims to replace
``dbapi.anonymous_session``.
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s specific hooks and operations"""