Raise the changed event in CzmlDataSource when CZML is loaded.

Also clarify the documentation in DataSource to indicate that the changed event should be raised when the name or clock changes.
Add an option to control whether the first data source added to Viewer automatically sets the clock.

Also improve the logic so that changes to the clock afterward, indicated by the DataSource changedEvent, update the clock as well.  Fixes #1134.
Don't fire changed event in CzmlDataSource unless clock or name have actually changed.
Update CHANGES.md
Merge remote-tracking branch 'origin/master' into fixDataSourceChanged

Conflicts:
	CHANGES.md
Fix Cesium.js generated file.

My recent changes to generate stubs caused the fileset for Cesium.js to be created too early, meaning that shader files could get left out if they were not present on disk before the build started.

Instead of the pathconvert hackery I was using before, I fixed our custom scriptdef tasks to work with file-based ResourceCollections instead of requiring a FileSet, so that we can use the <union> directly.
Merge remote-tracking branch 'origin/master' into fixDataSourceChanged

Conflicts:
	CHANGES.md
Update copyright year
Rearrange code to separate the DataSourceDisplay update from unrelated clock setting code.
Merge pull request #1371 from AnalyticalGraphicsInc/fixCesiumJs

Fix Cesium.js generated file.
Merge pull request #1367 from AnalyticalGraphicsInc/fixDataSourceChanged

Raise the changed event in CzmlDataSource when CZML is loaded.
Changes per review.
Merge remote-tracking branch 'origin/master' into issue1336

Conflicts:
	CHANGES.md