Revert changes to viewExtent. Move check for zero vector sooner and adjust if needed.
Update CHANGES.md.
Fix onDataSourceRemoved, and move onDataSourceChanged.
Viewer can now track which data source has the active clock.
Merge branch 'master' into viewExtent

Conflicts:
	CHANGES.md
Make "scale" private since it's an implementation detail.
Merge pull request #1442 from AnalyticalGraphicsInc/selection-api

Make "scale" private since it's an implementation detail.
Merge pull request #1436 from AnalyticalGraphicsInc/clock-tracking

Clock tracking
Fix non-webGL IE 11 specs.

This addresses all failing non-webGL IE 11 tests except for the DataCloneError failures related to web workers.
Merge pull request #1445 from AnalyticalGraphicsInc/ie11-noWebGL

Fix non-webGL IE 11 specs.
correct outline bounding sphere
Compatibility fixes to keep setup code from crashing in older browsers.
Switch back to global WebGLRenderingContext.
Merge pull request #1448 from AnalyticalGraphicsInc/ieFixes

Compatibility fixes to keep setup code from crashing in older browsers.
Remove redundant exception documentations

Each parameter is already marked as required as part of it's documentation, this removes the extra `@exception` documentation for it as well.

Fixes #1435
Merge pull request #1447 from AnalyticalGraphicsInc/polygonOnlineBoundingSphere

Correct PolygonOutlineGeometry bounding sphere
Merge branch 'master' into viewExtent

Conflicts:
	CHANGES.md
Add a couple more viewExtent tests.
Fix minor formatting errors.
Merge pull request #1449 from AnalyticalGraphicsInc/remove-redundant-documentation

Remove redundant exception documentations