fix _restructureLabel removed inner <label for="..."> tags

ex:
CakePHP original form helper output:
 <input name="data[test]" id="TestTest_" value="" type="hidden"><input name="data[test]" id="TestTestOne" value="One" type="radio"><label for="TestTestOne">One</label>
TwitterBootstrap form helper output:
 <label class="radio"><input name="data[test]" id="TestTest_" value="" type="hidden"><input name="data[test]" id="TestTestOne" value="One" type="radio">One</label>
Patched TwitterBootstrap form helper output:
 <label class="radio"><input name="data[test]" id="TestTest_" value="" type="hidden"><input name="data[test]" id="TestTestOne" value="One" type="radio"><label for="TestTestOne">One</label></label>