[UI] Labelling the interface

[andersonjeccel]

This PR adds documentation for better interface labels.

[RCheesley]

This looks great, a really good start! I have made a few comments but also I'd request we use quotation marks (" and ") only when indicating actual speech. For all others, use a single quote (' ') instead.

I agree in principle with the recommendations to remove all of the many ways that we use in the UI to indicate the same actions, and instead bring some consistency. This will, of course, have an impact on the translations so we might need to alert the translation teams to this when we merge the PR. It'll be quite a lot of work for them, I think.

[RCheesley]

Still outstanding comments here, plus conflicts to look at. Hopefully quick fixes though!

[RCheesley]

Deffo not a quick fix. Had to add labels for all the headings because they weren't being picked up by the build process.