Remove unused modules.
Merge pull request #1609 from AnalyticalGraphicsInc/removeUnused

Remove unused modules.
extent -> rectangle
Merge branch 'master' into renameExtent

Conflicts:
	Source/Workers/createVerticesFromHeightmap.js
update CHANGES.md
Merge pull request #1612 from AnalyticalGraphicsInc/renameExtent

Rename Extent to Rectangle
Merge branch 'master' into singleSceneEntry

Conflicts:
	CHANGES.md