Make automatic joining of groupchats optional
It should be possible to configure an account so that it doesn't automatically join groupchats (when starting Gajim and after every status change). It must configure that account only for a particular installation of Gajim, so it must not be stored on the XMPP server.
Rationale: If I idle in groups and connect through another resource, I get those annoying "do you want to join with a different nickname" popups. With this option, I could have a "main" resource which opens the groupschats automatically and keeps them open, and minor (e.g. temporary) resources which I use primarily for one-to-one chats.