Fix #356 - affine transform docs has the wrong direction of transform

[martinmodrak]

Submission Checklist

• Builds locally
• Declare copyright holder and open-source license: see below

Summary

Fixes #356 to show the correct direction of the affine transform when using offset or multiplier

Copyright and Licensing

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Institute of Microbiology of the Czech Academy of Sciences

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[bob-carpenter]

Thanks. Looks great.