Maven plugin name conventions

Hi,

as already argued on spice-dev for the metaclass plugin,
we should agree on a naming convention for the maven plugins.

The current convention is that maven-xxxx-plugin is the plugin for maven
of component/application xxxx.

Adopting this, the loom plugin for maven should be called
maven-loom-plugin.

This is also consistence with the dna plugin for maven.

If there are no objections, I'll go ahead and rename it.

Cheers