#54 Option to mute VBox/VNC Ext Pack message on every connection

[drwsrwx]

If the server doesn't have VirtualBox or VNC extension pack a warning message is shown every time the connection is established, even requiring user interaction. It's welcome to notify user, but in some scenarios this might not change, leaving user with annoying messages. One solution would be an additional setting to suppress the warning, or to simply show the message one time in any case.