chat: new chat selector: Using the new ScreenManager feature, a widget to select a chat to display is shown when a user opens the chat (except if an entity jid is specified, in which case it opens directly the Chat widget), or when user presses ESC. When on ChatSelector, pressing ESC brings to the root widget (i.e. default widget). The ChatSelect is a first draft, it is planned to show opened chats, rooms, and a way to create new chats.