Document configuration verify option and disable urllib3
In #28647 (moved) we say that it's ok that the destination certificate is self-signed. There was no any documentation about how sbws could accept self-signed certificates and the default was hard-coded. There're different ways to validate certificates with Python requests (http://docs.python-requests.org/en/master/user/advanced/#ssl-cert-verification), but the only one implemented is to don't verify the certificate. The simpler way to accept self-signed certificates is to don't verify it. When using this option, there're urllib3 warnings that should be disabled.