Internal utilities for maven plugin core dependency updates should stick to 3.x version for now

[mbien]

Some wizards and actions have to update or insert maven plugins into poms. Those typically will use the most recent version of that plugin if it is a "core" maven plugin.

This was a good default for a long time and made sure that new JDKs are automatically supported with the least maintenance required, but with mvn 4 around the corner it would be better to stick to 3.x versions for now (as quick fix). Later we should pick the best version for the used mvn version. (maven 4 plugins are were not intended for maven 3)