Add billboard rotation and aligned axis.
Merge branch 'master' into billboardRotation
Merge branch 'master' into billboardRotation
Merge branch 'master' into billboardRotation
Fix issue with vertical and horizontal origin. Add tests. Update Sandcastle example.
Update CHANGES.md.
Updates based on review.
Add conditional compilation in the vertex shader for billboard rotation.
Add custom width amd height to billboards.
Update CHANGES.md.
Updates based on review.
Update billboard Sandcastle example.
Merge pull request #859 from AnalyticalGraphicsInc/billboardRotation

Billboard Rotation
Merge branch 'master' of https://github.com/AnalyticalGraphicsInc/cesium into googleEarth