Clear tracked object when data sources are removed.
Material support for DynamicPolyline

Originally, we hardcoded DynamicPolyline to always us a PolylineOutline material type because we did not support general materials in CZML.  Now that the DynamicScene and CZML processing are decoupled, the lack of CZML support for it doesn't matter.  This allows users to use any Material we support in DynamicScene that also supports polylines (currently just ColorMaterialProperty and PolylineOutlineMaterialProperty but others are trivial to add).
Merge branch 'master' into let-go
Use new events to detect when a trackedObject has been removed and fly to home view when it happens.
Merge branch 'master' into let-go
Merge branch 'master' into let-go
Fix formatting.
Add specs for tracked object clearing.
Fixes to new unit tests.
Merge branch 'master' into dynamicPolyline-materials

Conflicts:
	CHANGES.md
	Source/DynamicScene/DynamicPolylineVisualizer.js
Fixes after merge.
Merge pull request #1117 from AnalyticalGraphicsInc/let-go

Clear tracked object when data sources are removed.
Merge branch 'master' into dynamicPolyline-materials
Fix my sloppy mistakes found during review.
Merge pull request #1168 from AnalyticalGraphicsInc/dynamicPolyline-materials

Material support for DynamicPolyline
Merge remote-tracking branch 'origin/master' into dynamicScene-fixes

Conflicts:
	CHANGES.md