function BillboardGroup()
{
	Mesh.call(this, new BufferGeometry(), new MeshBasicMaterial({depthWrite: false, colorWrite: false}));

	this.name = "billboard";
	this.type = "BillboardGroup";
}
Object that makes it rotation be the same as the camera.

It is rotated every frame before rendering to always face the camera direction.

@class BillboardGroup
@extends {Mesh}