Identifying camera/display overlays, better control over them

[amrytov]

Hello,

In a scene with multiple Robot nodes, especially if they are PROTOs or contain PROTOs, it is very easy to get multiple overlay windows in the 3D scene. There is no visual indication whatsoever that a particular overlay belongs to a specifc robot.

It would be very useful to have on the overlays either captions or a mouse hint pop-ups with information like "robot_name.device_name".

Also some API would be useful to control showing/hiding/positioning the overlays. Maybe a new Overlay(Device) node type which represents an overlay in the schema tree and can be added to a Display or a Camera. Then, actually, it would make sense to use overlay windows for any sensor device, to display whatever value(s) they return.