Missing points in documentation

[Pfeil]

The API is documented by examples and javadocs (the non-trivial-parts at least) and is pretty straight forward. But there is space for improvements, as far as I can see:

Developer docs

Parts of this are also interesting for users:

• How is import different from export, which class members store what in which case?
• How are invalid crates being handled on import? What is being tolerated (with warnings), what kind of invalid crates can we not import?
• When exactly are which parts being validated against what?
• We need a contribution.md which explains also the principles to ensure contributions are consistent (e.g., what to consider in builders etc)
• we need a release process to be documented and possibly tooling for it. Somesy can be used to keep the citation.cff up-to-date with another file, but gradle.properties is not yet supported. We can either use some script to invoke instead of gradle release with all required syncing boilerplate, and possibly contribute to somesy.

User docs

• We need a better Getting Started Guide, see for example Removing properties from entities is too complicated #41
• Arrays as properties, see Improve documentation around arrays as values of properties #216

[Pfeil]

Getting started has moved into unit tests to ensure we have executable and up-to-date examples. #256