Some updates and fixes

First of all, updated toxcore a bit (your last update causes project to fail build, so I did it again),
also updated MessagesTableViewController (before update I've seen black text on black input field, which is not very comfortable),
also I've corrected the incoming message to have origin set to `them` instead of `me` so now messages appears at left side and at the right side of the screen, as I would expect,
and added some constraint to make qrcode fit into screen.