Add Cesium.Cartesian3.lerp to externs.
Add Ellipsoid scaleToGeodeticSurface to externs.
Add Math.toDegree to Cesium externs.
Add terrain to main example.
Add IntersectionTests.rayEllipsoid and Ray.getPoint Cesium externs.
Add Billboard origin to Cesium externs.
Add Math.convertLongitudeRange to Cesium externs.
Add Cartesian3.clone to Cesium externs.
Have Globe.pick return non-null result in Cesium externs
Fix Ray type in Cesium externs.
More convenient camera orientation in Cesium externs.

Allows to simplify calling code.
Add globe depthTestAgainstTerrain to Cesium externs
Add CesiumTerrainProvider to Cesium externs