code: function (component) {
      var callbacks = this.callbacks;
      if (component.beforeStep) callbacks.beforeStep.push(component);
      if (component.step)       callbacks.step.push(component);
      if (component.afterStep)  callbacks.afterStep.push(component);
    }
docs: Adds a component instance to the system and schedules its update methods to be called
  the given phase.
  @param {Component} component
  @param {string} phase