- Add RenderStage enum for better control over when a Material should be
rendered
- Add getRenderStage method to Material
- Replace RenderLayerEvent with RenderStageEvent
- Pass more information to RenderContext including camera and projection
matrix
- Pass RenderContext instead of Camera to all beginFrame-related methods
- Remove RenderContext.CURRENT
- Remove FrustumMixin and CameraMixin
- Remove default BasicModelSupplier constructor
- Convert Material to interface and create SimpleMaterial implementation
- Move API instancer classes to instancer package
- Organize imports
