Memory management

Sceneview has several different memory ownership models, largely to reflect differing use cases.

In general, you should never need to explicitly call new or delete on any Sceneview classes.

• All classes derived from QObject or QWidget adhere to the Qt 5 ownership model.
• All nodes in a scene graph are owned directly by the scene itself (the sv::Scene object).
• All resources (Material, Geometry, Shader, Font) are managed with reference-counted shared pointers.