title: How can I put a placeholder text on ng-table select filter?
body: <p><strong>Code sample:</strong> <a href="https://plnkr.co/edit/hdYjHtEx1Dto1q6UVCS9" rel="nofollow">https://plnkr.co/edit/hdYjHtEx1Dto1q6UVCS9</a></p>
  
  <pre><code>$scope.idFilter = {
      id: {
        id: "number",
        placeholder: "Filter by id", // Working
      }
    };
  
    $scope.nameFilter = {
      id: {
        id: "text",
        placeholder: "Filter by name", // Working
      }
    };
  
    $scope.statusFilter = {
      status: {
        id: "select",
        placeholder: "Filter by status", // Not working
      }
    };
  </code></pre>
  
  <p>It is easy to add a placeholder on a number or text filters in ngTable. However I could not manage to find a solution for select filter. I know that placeholder on a 'select' element is not trivial by itself, but it is achievable.</p>
  
  <p>Can you find a solution for it in ngTable?<br>
  If not, can you recommend another table component that have this feature?</p>