This allows us to write doctests depending on a ui object, but not on global
configs.
ui.load() is a class method so we can do wsgiui.load(). All ui() calls but
for doctests are replaced with ui.load(). Some of them could be changed to
not load configs later.
And call it runservice() because I'll soon add createservice().
The main reason I'm going to introduce the 'server' module is to solve
future dependency cycle between chgserver.py and commandserver.py.
The 'server' module sits at the same layer as the cmdutil. I believe it's
generally good to get rid of things from the big cmdutil module.
Like the built-in HTTPS server, this code was using the ssl module
directly and only using TLS 1.0. Like the built-in HTTPS server,
we switch it to use sslutil.wrapserversocket() so it can follow better
practices.
Currently it only supports SMTP over SSL since SMTPS should be simpler than
handling StartTLS.
Since we don't need asynchronous server for our tests, it does TLS handshake
in blocking way. But asyncore is required by Python smtpd module.
