Modify Transforms.pointToWindowCoordinates and SceneTransforms.wgs84ToWindowCoordinates to return coordinates whre the origin is at the top left.
Update CHANGES.md.
Change from review.
Rename clipToWindowCoordinates -> clipToGLWindowCoordinates.
Make Billboard and Label pixelOffset origin be at the top left corner.
Update CHANGES.md.
Move pixel offset y coordinate negation from vertex shader to when writing to vertex buffer. Fix bug in bounding sphere computation.
Merge pull request #1862 from AnalyticalGraphicsInc/windowCoordinates

Window coordinates
Merge remote-tracking branch 'origin/master' into nodeServer

Conflicts:
	CHANGES.md