Introduce pubkey/unl tracking to Peer sessions. (#181)

* Adding pubkey in binary to comm sessions and is_unl flag to peer sessions.
* Removing display_name overloads and populating pubkey in user session.
* Changing peer session lookup key from uniqueid to pubkey (binary).

src/usr/usr.cpp

@@ -253,7 +253,8 @@ namespace usr
 
             session.mark_as_verified();       // Mark connection as a verified connection.
             session.issued_challenge.clear(); // Remove the stored challenge
-            session.uniqueid = pubkey;
+            session.uniqueid = pubkey_hex;
+            session.pubkey = pubkey;
 
             // Add the user to the global authed user list
             ctx.users.emplace(pubkey, usr::connected_user(session, pubkey, protocol));