updated KmlDataSource to reflect Sean's suggestions
updated KmlDataSource to reflect Sean's suggestions

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