Simplify application build process and application version management

Hey, I tried to simplify the application/Docker build and version management to make applying updates less error prone. This way it should only be necessary to update the application version in the 'revision' property of the parent POM which is then just referenced in the different Maven modules. Kind of a best practice from our projects. More information about this can be found here. Of course, it's still necessary to apply the version changes manually to Helm Chart, as long it's not automated. Hope the broken pipeline will be fixed this way.