[enhancement] split DeckScene keyframes up between layers and camera.

[chrisgervang]

Changes

• Instead of reserving camera key in keyframes object, give it a dedicated variable in DeckScene.
• For DeckScene construction, initialKeyframes split into cameraKeyframes and layerKeyframes.
• Added scene.setCameraKeyframes and scene.getCameraFrame

Renamed

• scene.setKeyframes to scene.setLayerKeyframes
• scene.getFrame to scene.getLayerFrame
• scene.keyframes to scene.layerKeyframes. Added scene.cameraKeyframes
• getKeyframes parameter renamed to getLayerKeyframes throughout DeckAdapter and examples.

[coveralls]

Pull Request Test Coverage Report for Build 950589590

• 0 of 24 (0.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 22.008%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
modules/core/src/adapters/deck-adapter.js	0	6	0.0%
modules/core/src/scene/deck-scene.js	0	18	0.0%

Files with Coverage Reduction	New Missed Lines	%
modules/core/src/scene/deck-scene.js	1	0%

Totals
Change from base Build 950454890:	-0.3%
Covered Lines:	139
Relevant Lines:	537

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💛 - Coveralls