Updates to jvnet-parent

...d.

- Remove versions from the plugin definitions, in order to allow consumers to use their own pluginManagement (don't enforce specific version of javadoc plugin).
- Remove enforcer execution from the default profile, instead putting it into the jvnet-release profile since it's only relevant for releasing.
- Add ${release.arguments} in the maven-release-plugin configuration to allow some customization.
- Isolate snapshots repository definition in a snapshot profile (in order to not allow snapshots by default), adding pluginRepository for snapshots
- Add new profiles for staging and promoted repositories
- Did not define pluginManagement section to manage plugin version, but that could be done
- Did not reformat the complete file, but some formatting might be incorrect.