Disable video output

[gavinhenderson]

Is your feature request related to a problem? Please describe.
Users don't always like to their own face when trying to setup EyeCommander

Describe the solution you'd like
We should allow users to disable the video stream. Although we should keep the lines painted on the canvas so the user has some visual feedback

Describe alternatives you've considered
This is similar to #47 but a simpler fist pass

Additional context
Message NG when done