Parametrize the possible SSL parameters of the server

This involves being able to set from a config file the various possible SSL options that such test helper may have. This includes:

• Which SSL version we should use
• Advertised cipher suite

We will be using pyOpenSSL and an example of setting some parameters and it's usage can be seen in tor2web: https://github.com/globaleaks/Tor2web-3.0/blob/master/run.py#L159