Telepathy multi-users chats (xmpp MUC, irc channels, etc)

[MerlijnWajer]

So locally I have support for basic channel support in Telepathy, and did some brainstorming...

Telepathy by default closes all channels if the handlers of the channels are gone, and it also doesn't automatically rejoin channels, also if the account just goes offline for a bit.

Things I (or we) will have to do:

1. Implement logging for channels
2. Implement overview of channels, maybe not mixed in with regular messages (I don't see the point).
3. In a channel window, use the channel/context QMenu to perhaps make a channel persistent (or mark it as non-persistent), which controls if we attempt to re-join the channel upon connection

[sanderfoobar]

1) we can maybe use rtcom column group_uid. 2) yeap 3) we'll need to store state somewhere, QSettings is an option (~/.config/conversations/settings.json)