Add pointCloudShading settings to fromGltf
Add pointCloudShading settings to fromGltf

likangning93/cesium,likangning93/cesium,likangning93/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,CesiumGS/cesium,CesiumGS/cesium,AnalyticalGraphicsInc/cesium,CesiumGS/cesium,CesiumGS/cesium,likangning93/cesium,likangning93/cesium