AnisotropyBarnLamp fixes & improvements

[echadwick-artist]

• UV seam fixed on flange near base, and all textures adjusted to match.
• anistropyStrength set to 1.
• anisotropyRotation set to zero, and erroneous array brackets removed.
• KHR_texture_basisu added to extensionsRequired for the KTX2 variant.
• Material and mesh names capitalized.
• Screenshots created with glTF Sample Viewer, which recently added anisotropy support.
• SBSAR graph supplied for normalizing anisotropy textures.
• Readme updated and expanded.

Please see https://github.com/KhronosGroup/glTF-Sample-Models/pull/366 for further details.