Prompt the user during install to enable the beta VersityGW WebGUI and, if accepted, append VGW_WEBUI_PORT=:7071 and VGW_WEBUI_NO_TLS=true to /etc/versitygw.d/gateway.conf. Update the installer to report that the WebGUI will be enabled and modify the completion script to display the WebGUI URL (http://<IP>:7071) when the config contains VGW_WEBUI_PORT. Keeps existing access/key generation and default gateway port unchanged.
