Support for X3D Volume component nodes

[brutzman]

Request validation support for X3D 4.0 Volume component.

• X3D 4.0 Architecture, clauwse 41 Volume rendering component
• https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-IS.proof/Part01/components/volume.html

Example models at

• X3D Example Archives: Basic, Volume Rendering
• https://www.web3d.org/x3d/content/examples/Basic/VolumeRendering

[michaliskambi]

Confirmed, I will do this, I want to add these new nodes (to validate, maybe even render -- at least basic modes of rendering 3D volumetric stuff should be easy to implement :) ).

I will not do this immediately, but please ping me if it takes me too long and it's urgent (just like about new sound nodes, #80 ).