refactor to allow changing our nick after nick conflict but first #967 needs to be fixed so I can test

systray.add_jid and systray.remove_jid now have another argument: the typ of message: ('gc' or 'chat' or 'single_chat' or 'pm')
systary now can handle pm messages

groupchat_window now has an on_message function that can hold pm in queues so they are not printed (systray is not handled yet)