Include CommonSurfaceShader in the official X3D specification

The CommonSurfaceShader node allows to easily use bump mapping, specular maps and other modern material features in X3D.

About CommonSurfaceShader:

• Castle Game Engine documentation: https://castle-engine.io/x3d_implementation_texturing_extensions.php#section_ext_common_surface_shader , contains also some comments about Instant Reality and X3DOM compatibility.
• Instant Reality documentation: http://doc.instantreality.org/tutorial/commonsurfaceshader/ , http://doc.instantreality.org/documentation/nodetype/CommonSurfaceShader/
• X3DOM documentation: https://doc.x3dom.org/author/Shaders/CommonSurfaceShader.html
• The original paper introducing the concept at Web3D 2010 conference: https://www.semanticscholar.org/paper/A-modern-declarative-surface-shader-for-X3D-Schwenk-Jung/e7775d93a1503e7496ece380ed93ae5bf2485dcf

CommonSurfaceShader also "covers" many use-cases where one may wonder about using shaders and multi-texturing. So it also makes explicit shader code less necessary (mitigating the need for "Programmable Shaders" component and my "Compositing shaders" extensions). They also make X3D multi-texturing nodes less necessary (mitigating the need to fix existing multi-texturing problems).