public static class DefaultContactEventHandler.RunMessageWindow
Runs the chat window for the specified contact. We examine different
cases here, depending on the chat window mode.
In mode "Open messages in new window" a new window is opened for the
given MetaContact if there's no opened window for it,
otherwise the existing chat window is made visible and focused.
In mode "Group messages in one chat window" a JTabbedPane is used to show
chats for different contacts in ona window. A new tab is opened for the
given MetaContact if there's no opened tab for it, otherwise
the existing chat tab is selected and focused.