Enable toggling of direct VNC server access.

[r-pufky]

By default, both ports 5800 and 5900 are exposed in the container. It would be fantastic to be able to add the option toggle the following port exposures:

• 5800 (VNC web GUI only)
• 5900 (VNC server only)
• 5800-5900 (both VNC web GUI, VNC server; current mode)

This would enable the selection of the preferred connection for an end user and minimize service exposure in the container.

[jlesage]

When using the default docker network mode Bridge, users need to explicitly expose the port(s) they want during the creation of the container.

[jlesage]

With images version 4.0.0, it's possible to disable listening on a port.