Add support for RealVNC VNC Viewer

[stefan_koell]

FYI: we created a KB article with troubleshooting tips for VNC connections:

Troubleshooting VNC Connections

VNC connections to macOS By default, macOS uses Apple Remote Desktop Authentication. Some VNC Viewers like RealVNC can handle Apple Remote Desktop Authentication; unfortunately, TightVNC which we use in Royal TS has not yet implemented Apple Remote Desktop Authentication. The solution to this issue is to set a VNC password. To do this, please go to “System Preferences - Sharing”. If Remote Management is turned on, turn it off. The reason for this is that you can’t have both Screen Sharing and R…