title: Knockout Mapping a foreach with another collection than the source
body: <p>I need to translate a text.</p>
  
  <p>This is my array of languages</p>
  
  <pre><code>[
     {iso:"fr",name:"French"},
     {iso:"en",name:"English"},
     {iso:"de",name:"German"},
  ]
  </code></pre>
  
  <p>My model</p>
  
  <pre><code>{
     translation :
     [
        {iso:"fr",content:"Bonjour"},
        {iso:"en",content:"Hello"}
     ]
  }
  </code></pre>
  
  <p>I'd like to have a form with all the languages displayed and my mapping would fill my translation model.</p>
  
  <p>Do you have any idea how I can do that with knockout ? Or any way to get near that ?</p>