Potential KML issues

[wallw-dev]

These are some items I noticed while testing the Cesium converter refactor:

• LineStrings (KML LineString Reference)
  • I don't think we are properly defaulting altitudeMode to clampToGround
  • I don't think we are properly reading tessellate, which should correspond to os.interpolate.Method.NONE if 0
  • For extruded LineStrings, the KML_Samples file has styles like "redLineBluePoly", which I think implies that there is both a line and a wall rendered by Google Earth. We only render the wall (this is more of a potential issue in the Cesium converter than in KML specifically)