#13 Create framework for scene graph management

[Mark Curtis]

A framework of classes needs to be created to manage scene rendering as a whole. Notes:

The scene is composed of a tree of scene nodes. Each node contains:
- Transform from parent
- Child nodes
- Leaf objects

Leaf objects that are supported by a scene node are:
- Renderables
- Hearables
- Cameras
- Regions
- Walkable (navmesh fragment)
- Animation affectors

Renderable is an interface used to bind together the following elements:
- Geometry
- Material
- Transform

Geometry is an interface for the following classes:
- Mesh
- Skin
- Polygon
- Particle emitter

Regions in an interface for the following classes:
- Click regions
- Camera regions
- Trigger regions
- Generic regions (used to query from scripts)