- Implement matching of fingerprints against servers.xml

 - Add support for fingerprints to servers.xml parser.
 - Add support for 'hidden' servers to servers.xml parser.
 - Add some fingerprints to servers.xml, for testing and as example for the new format.
 - Force asynchronous (nonblocking) SSL handshake in all case
 - Add logging to c/connection.py

Known issues:
 - Checking of fingerprints doesn't work on in-band SSL (Typically port 5222) because of stuff happening out of sequence. Workaround: use immediate SSL mode ("Legacy SSL" option in server config). Because there is as of yet no other way to /force/ SSL, this is also the most secure setting.
 - A lot of code is still looking for a better place to live.