Remember order of chats
Currently (as of ee799b9e) when I launch Gajim it opens (most of the time) the chats I had open in my last session.
I'm using Detached contact list with single chat, but this should apply to all window behaviors except Detached contact list with detached chats.
I would like Gajim to remember the order of chats (both single user chat and MUC) across sessions, so I don't have to reorder them every time I launch them.
I'm guessing it's currently based on the order Gajim learns about the contact when it's sent by the server, as it seems to be consistent across restarts.