Handle two way binding with nested properties

Handle nested props with two way binding:

<script id="app-template" type="text/stache">
  <home-page textData.textValue:bind="textString" />
  <input value:bind="textString"/>
</script>
  
<script id="home-template" type="text/stache">
  <h1>Home Page</h1>
  <input value:bind="textData.textValue" />
</script>a

Resolves - canjs/can-stache#408