Introduced new attribute XCAFDoc_VisMaterial storing visualization material definition.
XCAFPrs_Style has been exteneded Material() property.
XCAFPrs_AISObject::DispatchStyles() maps new XCAFPrs_Style::Material() property onto graphics aspects.
RWGltf_GltfJsonParser and RWObj_CafReader now put Material definition into XCAF document instead of a color label.
RWGltf_MaterialMetallicRoughness - added missing properties AlphaMode, AlphaCutOff and IsDoubleSided;
fixed default values in constructor for Metallic and Roughness.
Added commands XGetAllVisMaterials, XGetVisMaterial, XAddVisMaterial,
XRemoveVisMaterial, XSetVisMaterial, XUnsetVisMaterial for working with
new visualization materials table in the document.
