One of the methods was duplicated. Additionally, apply a very few coding standards.

Remove logging of callback method calls. Such cross-cutting concerns are better directly implemented in the xmpp dispatcher.

Plan is to move our ConnectionX classess to the protocol package one by one. Each move should be more than a simple copy paste. It should be preceeded by cleanups and the like.

 * Make it testable and write a very basic test for the presenceCallback
 * Use Extract Method to make the code more readable and to increase reusability
 * Start to decouple ConnectionCaps from the other Connection classes/handlers

Missed to reflect API changes in the tests.

gc_contact.jid and gc_contact.resource are empty in anonymous rooms. In non-anonymous rooms those contain the real jid and resource of the contact.
We must not mix those information with the jid of the contact in the groupchat: We assumed that "test@conference.gajim.org/nick" was the Jid and 'someresource' the resource. So we tried to talk to 'test@conference.gajim.org/nick/someresource'.

re-enable the ability to connect as invisible: check that we don't send presence with show=invisible at the correct place, after we diferenciate invisible conection from not-invisible connection. Fixes #5473

update README file to depend on python-dbus >=0.81, which is needed for bus.list_names() function. Fixes #5474