3.3.0 version of Maven plugin for Acceleo + pom.xml upgrade

Following this thread : https://github.com/eclipse/acceleo/commit/be33165c0661b3a676f6b9ed655bb144ec81c2fa#commitcomment-1615572, here is the 3.3.0 version of the maven plugin pushed into repository and suggestions for upgraded pom.xml.

Regards,

Laurent