Renamed vec3 -> Vec3, changed associated functions to methods.
Renamed mtx33 -> Mtx33, changed some functions to methods.
Fixed many warnings.
Renamed light->Light, make_light->Light::new
Also removed pub from generate_raytraced_image_{single,multi}
Renamed:
  polysoup->Polysoup
  mesh->Mesh
  kd_tree->KdTree
  axis->Axis
  kd_tree_node->KdTreeNode
  x->AxisX
  y->AxisY
  z->AxisZ
  leaf->KdLeaf
  node->KdNode
Renamed intersection->Intersection
Renamed rand_env -> RandEnv
Renamed aabb->BoundingBox