title: Knockout how to remove items from select dropdown if it is already selected in previous or next row
body: <p>I have three rows here. First dropdown should displays all the names. If I select a name from the first dropdown, next dropdown should not contain the name selected in the first dropdown.</p>
  
  <p>For eg. If I have {Peter,John,Michael}, first drop should show all three options. If I select Peter in the first dropdown, next row dropdown should only show {John,Michael}. If I select John in the second dropdown, final dropdown should only contain Michael.</p>
  
  <pre><code>&lt;table&gt;
       &lt;tbody data-bind="foreach: Items"&gt;
           &lt;tr&gt;
               &lt;td&gt;
                   &lt;select data-bind="options: $root.Persons, optionsText: 'name', event :{ change: $parent.SelectionChanged }" /&gt;
               &lt;/td&gt;
             &lt;/tr&gt;
    &lt;/tbody&gt;
  &lt;/table&gt;
  </code></pre>