* Improve naming for root scene graph switch/separator nodes.
* Improve scene graph inspector.
This commit improves the scene graph inspector by improving the UI
layout and displaying information in a more human-readable way.
Instead of having a main generic string column for all node-specific
data, introduce specific columns for node name, memory address and data.
Better visualization was also added for `SoDrawStyle`, `SoPickStyle`
and `SoCoordinate3` node types.
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