Allow tweaking release arguments form the CLI

* We need to provide a default empty value for the 'arguments' property within the pom
  This ensures that when the property is not provided, the build can still continue
* The `arguments` property is especially useful if you don't have the GPG key for
  signing as you can then test the release process by adding

    -Darguments=-Dgpg.skip=true

  to the command line used to prototype a release and the verification build will succeed.