Pass Hooke instance to CommandEngine.run(), not UserInterface.run().

Pass Hooke instance to CommandEngine.run(), not UserInterface.run().

User interface just needs its configuration (already setup in
  Hooke.load_ui() -> ui.load_ui(self.config)
) and a read-only list of commands.  Giving the Hooke instance to
CommandEngine allows the commands to work on the Hooke instance
directly.  This makes user interfaces less intelligent (i.e. easier to
write), and more consistent (because they all depend on the same
commands engine.)