Support for cameras stored in the GLB file

[mvaligursky]

• Implements camera part of the specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
• Note that cameras (CameraComponent) is disabled when loaded, it's up to the user to enable as needed
• Fixes Support for glTF cameras #2062
• Uses code from Support for glTF scenes, cameras and lights #2385, thanks @godiagonal !
• Engine example Glb Loader was changed to demonstrate this - it loads glb with geometry, lights and cameras, and switches between loaded cameras (one perspective, another orthographic)