Have a case class extend this trait for its fields to become command line arguments, and its body the core of your app using these.
Have a singleton extends this class to get a class with a main method for the app of
Have a sealed trait extend this for its case class children to become commands.
(Since version 1.2.0-M2) Use CommandApp instead
(Since version 1.2.0-M2) Use CommandAppWithPreCommand instead