title: Datatables serverside search and sort with alias
body: <p>Congrats for DT. Awesome job. 
  I have one situation here:
  Using server-side, i need using  "alias" for columns, because the join is at same table:</p>
  
  <p>Table location
  Location source
  Location destiny</p>
  
  <p><strong>So, in $joinQuery:</strong>
  ..</p>
  
  <pre><code>LEFT JOIN localidad GO ON A.mxv_loc_ori_fk = GO.loc_id
  LEFT JOIN localidad GD ON A.mxv_loc_dest_fk = GD.loc_id
  </code></pre>
  
  <p>..</p>
  
  <p><strong>And, in $columns:</strong></p>
  
  <pre><code>array(
         array( 'db' =&gt; '(`GO`.`loc_nombre`) as origen', 'dt' =&gt; "origen", 'field' =&gt; 'origen'),
         array( 'db' =&gt; '(`GD`.`loc_nombre`) as destino', 'dt' =&gt; 'destino', 'field' =&gt; 'destino' )
  );
  </code></pre>
  
  <p>**And, in JS: **</p>
  
  <pre><code>"columns": [
      {"data":"origen"},
      {"data":"destino"}
  ]
  </code></pre>
  
  <p>ALL GOOD at this point! The columns show the info correctly.
  The problem is at the moment at i try to SEARCH and FILTER. 
  I cannot understand why, but it doesn't work!</p>
  
  <p>Please help!</p>