detection code

Don't change sleeper state when we send a presence to a user, to not think global status has changed from invisible. see #4631

Introduce a get_instance factory method for all plugins and other xmpp related classes. This will help us to decouple plugs in order to make them testable.

Switch to SSL version 3 as the channel encryption protocol. As of http://docs.python.org/dev/library/ssl.html this is the maximally compatible SSL variant.

Proposed Fix. Make sure we read all data from our SSL socket wrappers and don't just rely on gobject.io_add_watch, select or poll.

This isn't really a clean solution, but the less intrusives fix that I can think of. Fixes #2634.

 * Use namespace instead of attrs={} for addChild
 * Unplug SASL module on auth failure (we currently disconnect so don't really need it)

Coding standards and documentation improvements in dispatcher_nb.py. Many open questions remain at my side. Please check FIXMEs.