4.2 / 4.3 (proposal) : add NGINX exemples

[JulienWilhelm]

In these criteria, we only provide exemples for Apache2 (with .htaccess). First, it should be precised that these examples concern Apache2. Second, we could add examples for NGINX.

[AlexDawsonUK]

As we're trying to keep to one example per guideline (to avoid overwhelming the spec), I've added links to NGINX boilerplates within the text (so that individuals can choose their environment). This will be reflected in the next draft.

[AlexDawsonUK]

Note: I've just been alerted to that I missed one of the NGINX links in an Apache code reference.
This will be resolved within the next draft of the specification.