title: Angular dynamic form, sub-components not updating top level form
body: <p>As the title suggests, I've created a dynamic form using a mix of tutorials I've read. 
  I have a parent component which creates a empty form group which I then (try) to populate with sub-groups via child components. These components are passed a reference to the parent form, and the child component then creates its own formgroup and attempts to bind this to the parent. </p>
  
  <p>The form model should then look like the following:</p>
  
  <p><code>FormGroup
  -- FormGroup1
  ---- FormControl1
  ---- FormControl2
  -- FormGroup2
  ---- FormControl3
  ---- FormControl4</code></p>
  
  <p>However, even thought the lower level form controls all render, the parent form doesn't seem to know they exist. My issue seems like it might be related to <a href="https://stackoverflow.com/questions/43399022/angular-2-how-to-link-form-elements-across-a-dynamically-created-components">Angular 2: How to link form elements across a dynamically created components?</a> but I was unable to figure out what he actually did to fix his issue. </p>
  
  <p>Any thoughts?</p>
  
  <p>See <a href="https://stackblitz.com/edit/angular-imi6j6?file=app%2Fapp.component.html" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-imi6j6?file=app%2Fapp.component.html</a> for what I'm doing.</p>