Ellipse with a height incorrect across IDL in 2D and CV

Reported on the forum: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/H7dMIe1_k2Y

The ellipse is correct at height: 0. Anything higher than that causes the ellipse to triangulate incorrectly. The larger the height, the more noticeable the error is.


``` javascript
var viewer = new Cesium.Viewer('cesiumContainer', {
sceneMode : Cesium.SceneMode.SCENE2D
});

viewer.entities.add({
position: new Cesium.Cartesian3.fromDegrees(-166.2117, 32.5805, 823373),
ellipse : {
semiMinorAxis : 1426124.013,
semiMajorAxis : 1426124.013,
material : Cesium.Color.WHITE.withAlpha(0.7),
height: 2000000
}
});

viewer.entities.add({
polyline : {
positions : Cesium.Cartesian3.fromDegreesArray([-179.8, 55, -179.8, 15])
}
});

viewer.zoomTo(viewer.entities);
```

Start with the JavaScript reproduction in the issue, using the Cesium.Viewer sceneMode SCENE2D and the entity ellipse with a nonzero height. Compare the rendered ellipse at height 0 and above it, including the reported 2D and CV cases; done means the ellipse triangulates correctly across the IDL at elevated heights.

Written by the indexing model from the issue text.