title: angular-formly data binding between repeating sections
body: <p>I'm attempting to make a dynamic form that uses live data from other fields in a cascade from max_points to 0. </p>
  
  <p>Each row has a high and low range, and the high range of the next form is always the low_range of the previous-1.</p>
  
  <p>I'm having trouble with how to manipulate the model data in a field setting. Moreover, I'm a little confused about how to access the larger data model on the scope of each field:</p>
  
  <pre><code>{
     type: 'input',
     //want to bind this field to the previous index's low_range -1  
     key: 'high_range',
     className: 'col-xs-4',
     templateOptions: {
       label: 'High Range',
       disabled: true 
     }
     controller: function($scope) {
        //I have access to the element this corresponds to, but haven't found a way to lookup this element in the larger model array
     }
  }
  </code></pre>
  
  <p>Ideally the high range of the first element would be max_points, then each one after would reference the previous low_range</p>
  
  <p>here is my live example: <a href="http://jsbin.com/behosokoye/edit" rel="nofollow">http://jsbin.com/behosokoye/edit</a></p>