[Twisted-Python] Checking in SSL support

[Itamar]

Ok, I have basic working SSL support. I also made an echoserv-ssl.py so 
I could test the code. I can telnet-ssl in and get data echoed back.

May I checkin the following?
1) twisted.internet.ssl
2) docs/examples/echoserv-ssl.py
3) docs/examples/server.pem (a SSL ceritificate so echoserv-ssl can run).

SSL contexts are created per socket and not stored in the 
ssl.Port/ssl.Client instances, since they are not picklable.