Start of Credit optimizations
Fix Credit.equals
Optimize CreditDisplay.addCredit
Merge remote-tracking branch 'origin/master' into credit
Updated based on review
Merge remote-tracking branch 'origin/master' into credit
Standard Entity default orientation support.

1. Added a new private (for now) function, `Entity._getModelMatrix` to
centralize creating a modelMatrix from an entity instance. This function
is the same as the `ModelVisualizer` behavior, which defaults to ENU
when no orientation is provided.

2. Refactored `ModelVisualizer`, `EllipsoidGraphics`, and
`CylinderGraphics` to all use `Entity._getModelMatrix`.
Remove dead code.

These private functions are from an old implementation of the property system that is no longer used.
`createPropertyDescriptor` now handles this automatically.
Merge pull request #2356 from AnalyticalGraphicsInc/remove-dead-code

Remove dead code.
Merge remote-tracking branch 'origin/master' into default-orientation
Merge pull request #2355 from AnalyticalGraphicsInc/default-orientation

Standardize default Entity orientation.
Merge pull request #2345 from AnalyticalGraphicsInc/credit

Optimize CreditDisplay
Merge remote-tracking branch 'origin/master' into polygongraphics-holes
Merge branch 'polygongraphics-holes' into implicit-properties

Conflicts:
	Source/DataSources/Entity.js