Make modules further indepenet from parent pom

[marpet]

Currently, all sub-modules depend on the parent. The dependencies are all managed in the parent.
This still forces us to use common versioning.
The usage of a BOM helps to reduce this dependency. But still, the dependency management is done in one place.
https://howtodoinjava.com/maven/maven-bom-bill-of-materials-dependency/

An open question is still, how to deal with the plugin configurations. Maybe they need to be shifted into the submodules.

Afterward, the modules can be developed independently from each other.