Fix NxTransformations matrix order

[matthew-d-jones]

If a transformation depends on another, the one it depends on should be applied first and should therefore be further to the right in the expression for T_f. Therefore, in the NxTransformation documentation this does not look correct to me:

For a chain of three transformations, where T_1 depends on T_2 and that in turn depends on T_3, the final transformation T_f is
T_f = T_3 T_2 T_1

Please check I have not misunderstood the existing documentation before merging!

[PeterC-DLS]

The depends_on chain is physical not mathematical. So the ordering is different for passive transformations.

[prjemian]

@PeterC-DLS: Can you supply a few words to clarify so others are not also unclear?

[PeterC-DLS]

The difference between active and passive transformations are the former moves things in a fixed coordinate frame whereas the latter is changing between coordinate frames.

To interpret information from, for example, a detector (say a pixel location), we are transforming from the detector's frame via each positioner to the laboratory frame fixed to the last positioner that depends on ".".

[matthew-d-jones]

@PeterC-DLS Thank you, makes sense. I will create a new PR for just the equation rendering fixes.
It is explained quite clearly on the design page actually, perhaps I can link to that from the class definition.

[matthew-d-jones]

Created #604 for the rendering fixes.