fix for #950

[FrankHossfeld]

This PR fixes the issue #950 & #227.

Changes:

• add a dependency management to the parent pom
• add a plugin management to the parent pom
• remove all version-tags from dependencies that are managed inside the dependencyManagement and plugins that are managed inside the pluginManagement in the child pom (library & validator & cli)
• remove the maven-shade-plugin (library-module-pom)
• remove the maven-shade-plugin (validator-module-pom)
• add main class in the maven-shade-plugin of the cli pom
• add two dependencies to avoid the CNFE while running the cli (Uber-Jar - Warum? #227)

After merging, no shaded library will be needed.

[jstaerk]

I have become cautious with changes in the POM, is it OK when I merge after the next release and would you be available to release the version after the next one together? We would do a ~1h online meeting so that we can interactively either correct or roll back changes. I did the same with the @langfr 's POM changes and that was super helpful, so far the maven central release process was not very stable towards ... unexpected changes (which could not be tested in advance anyway).

[FrankHossfeld]

@jstaerk Sure, it is. I'll need to update the PR first. Then, in case you are interested, we can try to merge it.

"so far the maven central release process was not very stable towards" ... that sounds like the repo needs a better CI/CD. Looking at the things GitHub offers, there are a multitude of possibilities to improve CI/CD. And it does not take much. So, why not improve the branch concept, use some actions and create an automated build and deploy for SNAPSHOT? What do you think? (Of course, this will be a new issue or two ...)

In my opinion, the shaded plugin creates a lot of problems. Maybe that's the reason why you are running into.

[FrankHossfeld]

@jstaerk Due to changes related the use of Maven Central (https://central.sonatype.org/publish/maven-central-publishing-limits/) it might also be a good idea to drop using shaded jars.