Adding film aspect ratio output blanking (or crop) for each displays

[laclaumatthieu]

For editors, it would be very convenient to be able to crop the image and put black bars on monitors.
Ideally, we could add automatically add black bars for those aspect ratio: 1:1.33. 1:1.5, 1:1.66, 1:1., 1:1.78, 1:1.85, 1:2.0, 1:2.35, 1:2.39.
Thanks.