title: Nightwatch Page Object hierarchy/re-use
body: <p>I'd like to use Nightwatch's Page Objects system for UI components used across our app. Because nightwatch has their own way of reading/initializing them, I don't see a way of properly extending/re-using them.</p>
  
  <p>For example I want an <code>DateInputPageObject</code> for "date fields". It would identify the label, input, date picker, etc.</p>
  
  <p>I'd use it on any page with a date input field.</p>
  
  <p>I would also like to extend page objects. For example, <code>class FooModal extends Modal</code>. The <code>ModalPageObject</code> would define selectors for elements all modals have - the overlay, container, close button, etc.</p>
  
  <p>I can't find any way to do this in nightwatch, is it possible at all?</p>