Show view-specific Bing attribution.
Better mechanism for obtaining credits.
Handle the possibility that no attribution is provided.
Add getTileCredits to all imagery providers.
Update tests with updated URL.
Remove useless comment.
Move terrain/imagery credit update to surface.
Use defaultValue.EMPTY_OBJECT instead of allocating.
Merge remote-tracking branch 'origin/master' into bingAttribution

Conflicts:
	CHANGES.md
	Source/Scene/CentralBody.js
	Source/Scene/CentralBodySurface.js
Fix error path when loading image via blob.

Returning an error from a error callback puts the code back on the success path, which is not what we want.
Make credits smaller and don't wrap them in the middle.
Merge pull request #1440 from AnalyticalGraphicsInc/tileLoadFixes

Fix a few minor issues in the tile load code
Re-add provider-level credits.
Update CHANGES.md.
Merge pull request #1338 from AnalyticalGraphicsInc/bingAttribution

Display attribution for the Bing Maps tiles displayed in the current view.
Merge remote-tracking branch 'origin/master' into performanceNow

Conflicts:
	CHANGES.md