NGINXaaS - Reorganize Changelog

[russokj]

Overview

Need to get rid of the top level Changelog archive.

Description

Would like to see the Changelog archive moved under Changelog at the bottom of the list, and renamed to Archive.

In addition, under Changelog, some of the entries have a What's New subsection. Please remove those as every changelog has something "new", so it's redundant (either that, or we add a lot more of these subsections).

Acceptance criteria

Consistent approach is used for all changelog entries and the the top level of the NGINXaaS for Azure has a cleaner look.