Start creating a very simple CesiumWidget to replace the Dojo-based one.
Switch Sandcastle examples to new standalone CesiumWidget.
Merge branch 'master' into cesium-widget
Merge remote-tracking branch 'origin/master' into cesium-widget

Conflicts:
	build.xml
Merge branch 'master' into cesium-widget
Move CesiumWidget into its own subdirectory to be consistent with other widgets.
Some minor widget tweaks.  Major changes to come.
Merge branch 'master' into cesium-widget
Fix Billboard.computeScreenSpacePosition.
Update CHANGES.md.
Merge branch 'master' into computeScreenSpacePosition

Conflicts:
	CHANGES.md
first pass at terrainSample contrib
fix formatting issue
support for for reading dynamic ellipse information through czml.
fix formatting in CZMLDefaults.js.
Update CHANGES.md.
Enable terrain depth testing.
Fix JSHint warnings, and other minor cleanup.
Refactor terrainSample function.

Mostly I moved some of the interpolation functionality into
`HeightmapTerrainData`, and used some fancy features of the promise
library to avoid manually tracking tile completion.
place marker closer to everest peak