Added skyBoxSources option
Merge remote-tracking branch 'origin/master' into skybox
Improved skybox after review
Updated doc
Merge remote-tracking branch 'origin/master' into skybox
Merge master to skybox
Merge master to skybox
Merge master to skybox
Merge remote-tracking branch 'origin/master' into skybox
Merge remote-tracking branch 'origin/master' into skybox
Merge remote-tracking branch 'origin/master' into skybox
Changes based on review
Merge master to skybox
Merge remote-tracking branch 'origin/master' into skybox

Conflicts:
	CHANGES.md
Merge pull request #1196 from AnalyticalGraphicsInc/skybox

Added skyBoxSources to the CesiumWidget and Viewer constructors