Unify formatting and update formatting config

[manuel-mauky]

At the moment we have a formatter config based on eclipse-settings. However, in the development team there are not eclipse users anymore but only IntelliJ users.

Even though there is a formatter config, not all files are formatted uniformly. To fix this, we should work on the following issues:

• [ ] Evaluate more general editor configuration formats like https://editorconfig.org/. Even cooler would something like https://github.com/jhipster/prettier-java.
• [ ] Create a new config for formatter settings
• [ ] Reformat all existing code files with the new formatter settings
• [ ] Work on automated checking and formatting as part of the build-process or Pull-Requests