title: select option template binding to index of array
body: <p>Am I able to bind the optionsValue of a select list to the index of 
  the particular item in the option array? </p>
  
  <pre><code>&lt;select data-bind="options: options,  optionsText: 'text', 
  optionsValue: ko.utils.arrayIndexOf(**somevalue**)" /&gt; 
  </code></pre>
  
  <p>Or am I stuck with having to transform my options object from </p>
  
  <pre><code>{ 
      text: 'asdasd' 
  } 
  </code></pre>
  
  <p>to </p>
  
  <pre><code>{ 
     text: 'asdasd', 
     id: 0 
  } 
  </code></pre>
  
  <p>and doing </p>
  
  <pre><code>&lt;select data-bind="options: options,  optionsText: 'text', 
  optionsValue: 'id' /&gt; 
  </code></pre>
  
  <p>Thanks </p>