Reduce over-width diagrams (#49)

* Reduce over-width diagrams

TRC diagram simplified and reduced to 72 characters width.
Figure 3 was identical and superfluous so has been replaced with a reference to the revised Figure 2.

* Reformatted pseudo-code

* Fix formatting error in pseudo-code

* More formatting fixes

* Updated TRC diagram

* Updated security goal in Intro

* shorten sentence

* changelog

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Co-authored-by: Nicola Rustignoli <[email protected]>