Recomended JAR plugin config is incorrect

[pavelhoral]

We have advocated switching from packaging components via maven-bundle-plugin to maven-jar-plugin. The main motivation was to have MANIFEST.MF with OSGi configuration ready for lifecycle phases before package and to drop custom packaging that was not that well supported in Eclipse.

However the suggested configuration (as declared in README.md of this project) configures JAR plugin in a way that is incompatible with test-jar goal (we don't want test-jar to use custom manifest or even worse - manifest of the main artefact). This needs to be addressed and the change has to be propagated to child projects...