Add support for specifying the local maven repo with "maven.repo.local"

[flow (Florian Schmaus)]

@mark_vieira

In the mean time you might want to consider using the ‘maven-publish’ plugin instead.

I’d be happy to switch to the new ‘maven-publish’ plugin. What hinders me is a detailed migration guide, so I can migrate my project from the ‘maven’ to the ‘maven-publish’ plugin.