fix for fprg

    I got problem when i make collection for my form. My collection has target_element which can be added few times. I use fileprg because this form also contains file inputs. 
    When we use form without fileprg plugin everything is fine and added elements to collection are validated but after we make form with fileprg plus we have new elements added to collection, those new elements are not validated at all. I dig in and realized that getInputFilter() function in handleGetRequest() doesnt add InputFilters to form for new elements. It doesnt know about it because form only contains information from the configuration of form. If we set 'count'  => 1 in options of collection it will validate only first element.