Add tab completion to groupchats

Most of the reason I don't leave qTox running all the time is because its chat area is so much suckier than my irc client, like for the same space quassel gets twice as many lines (and I can paste things from it too lol).


So, in this case at least, the mockup is wrong. :) Frankly, is there any other chat program at all on this planet that does that?