[fw-mvc] File element for Zend_Dojo_Form

Zend_Dojo_Form has elements like Button, CheckBox, RadioButton,
SimpleTextarea which implement the same functionality as regular
Zend_Form elements but allow you to keep you form elements in the same
style/theme. Although there is Zend_Form_Element_File I haven't found
an equivalent for Zend_Dojo_Form. It would be nice to have it.