Provides detailed information about Ranch listeners

Ranch now depends on SSL. Users embedding listeners in
their supervision tree are expected to depend on SSL too
if they are using it.

We always get the acceptor to resume. The child process will
be killed, and the current code will ignore any EXIT message
when that happens because the pid isn't in the process dictionary.

Simplify some return values, improve error messages for
eaddrinuse and no_cert.

Amended to add tests and simpler code. Also hides the
contents of cert and key transport options, if any.

Cert/certfile is no longer required if SNI options are provided.

Dialyzer will still complain about unknown options, but at
least users won't be stuck waiting for an upstream update.