Handle network errors

- Move HTTP connect/disconnect logic to networkManager
- If a talk fails due to socket error, HTTP transport error or
  nio bad response that might change, retry every 2s until success
- Clean up some leftover debug prints

TODO.md

@@ -7,8 +7,6 @@
   it should be the peer's display name instead.
 - Support "Empty room (was ...)" after peer left
 
-- Catch network errors in socket operations
-
 - Proper logoff when closing client
 
 - Handle cases where an avatar char is # or @ (#alias room, @user\_id)