Clarify order in which matrix and transform are applied from ChunkTransformationMatrix

[dstansby]

Your idea

ChunkTransformationMatrix is a:

3x3 or 4x4 affine transformation matrix describing spatial chunk transformation, for 2D and 3D respectively.

As I understand this encodes an affine transform in the [0:2, 0:2] or [0:3, 0:3] items of the matrix, and then a translation in the [3, 0:2] or [4, 0:3] items of the matrix.

It is not clear whether the translation is applied before or after the affine matrix however. It would be good to clarify this in the glossary for ChunkTransformationMatrix.