GUI: connection dialog must remember recently used servers

User can use a special button to select recently used server from a popup list (server, port and user name). It can be combined with predefined list too.

Start by locating the GUI connection dialog and the existing predefined-server list or popup implementation. Determine how server, port, and user name are currently entered, then define completion as being able to select a recently used server and optionally combine it with the predefined list.

Written by the indexing model from the issue text.