Fix DynamicObjectView offset across scenes and from viewFrom DynamicObject property.
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.
Merge branch 'master' into viewFrom
Don't destroy user-specified DataSourceCollection.

When Viewer is destroyed, it should only destroy its DataSourceCollection
if it created it.  A user-supplied DataSourceCollection is owned by the
user.
Merge pull request #1863 from AnalyticalGraphicsInc/viewerDeletesDataSourceCollection

Viewer should not destroy user-specified DataSourceCollection
Move pixel offset y coordinate negation from vertex shader to when writing to vertex buffer. Fix bug in bounding sphere computation.
Changes based on review.
Merge pull request #1857 from AnalyticalGraphicsInc/viewFrom

Fix DynamicObject.viewFrom
Merge pull request #1862 from AnalyticalGraphicsInc/windowCoordinates

Window coordinates