Due to recent core changes we now need to store a peer's
previous name instead of relying on API lookups via the
peer_id in the name change callback in order to display
the correct info
This takes into account the possibility of multiple peers in
the group using the same nick. The /whois command now lists
all peers associated with the input name, and all commands
that target a peer with a non-unique nick will require the
public key to be used.
