Update documentation and changelogs

[punycode]

The current project documentation is confusing for people, that want to start working on a CoffeeNet-enabled application. There is no stated purpose of the project, no clear structure, the main README.md is mostly links to other README.md files and a architecture diagram, that only documents the structure of the Maven dependencies for this multi-module project…

What we need is:

• A simple entry-README.md stating what CoffeeNet is about and how to get started
  • The reason why it exists
  • Explaining what it provides on top of Spring Boot
  • A minimal example for a Maven-based CoffeeNet POM on top of a Spring Boot project
  • Information for contributors, how to use issues und pull-requests to add new features
  • Information for maintainers, how CoffeeNet is built and released, including the used services (e.g. Github Actions, Sonarcloud)
• A real docs folder, explaining the different modular parts of CoffeeNet and how they are used
  • What the module does
  • How to use the module in your project
  • Any configuration properties that are available
• A CHANGELOG.md that records the issues and pull-requests between releases and if they are breaking changes, how to migrate