Follow on to #753.

Since we now support full 3D affine transforms, and these transforms should be represented in 3D by a set of three colored arrows, the arrows should represent not just the rigid transform but also shearing and scaling. For instance:

• If the transform involves scaling in the x-axis by a factor of 2, the red arrow should be two times longer than the other two.
• If the transform isn't orthogonal, the arrows shouldn't be orthogonal either.
• If one transform scales points uniformly by a factor of 2, and another transform is a pure rotation, the three arrows of the first should be two times as long as the three arrows of the second.
  • Corollary: Any configurable sizing of the transforms should be set globally for the whole view.
  • It may be difficult to have these make sense to express in screen space sizes.