Add support for the EXT_frag_depth extension.
Update CHANGES.md.
Merge pull request #1191 from AnalyticalGraphicsInc/EXT_frag_depth

EXT_frag_depth
Merge branch 'master' into dynamicObject-name

Conflicts:
	CHANGES.md
Add back optional name property.
Merge branch 'master' into dataSourceBrowser
Merge branch 'master' into dynamicObject-name
Merge branch 'master' into dynamicObject-parent
Merge branch 'master' into kml
Merge branch 'kml' into uberbranch
Merge branch 'dynamicObject-parent' into uberbranch
Merge branch 'dynamicObject-name' into uberbranch

Conflicts:
	Source/DynamicScene/CzmlDataSource.js
Merge branch 'dataSourceBrowser' into uberbranch