Data Exchange - Handle whichChoice / choice in VRML 2.0 Switch node

Current VrmlData_Scene / VrmlData_Group doesn't support the Switch node from VRML 2.0 standard and gives VrmlFormatError.

Example usage of Switch node:

Group {
  children 
    Switch {
      whichChoice 0
      choice [ 
        Shape {
          ...
        },
          
        Shape {
          ...
        },
          
        Group {
          ...
        } ]
    }
}

Example files and patch are attached.

It is ok to push the patch without CLA.