Add hints that both users need to scan each other's QR codes/add each other's links
This branch is intended as a workaround for usability issues with adding contacts (nearby and at a distance). Info boxes are added to the UI to explain that both users need to scan each other's QR codes or add each other's links.
These changes may conflict with !1722 (merged), in which case I'm happy to go with whichever solution works better, or use both.