customization of upload package input in admin interface

now this control has the same appearance in different browsers (tested in Chrome - last version, Firefox - last version, Opera - last version, IE10, IE9, IE8 but it should work also in IE7 and previous versions of Ch, Ff, Op) and it is better integrated in bootstrap form.  The functions of origin control are preserved, therefore in Chrome and Firefox we can also drag-and-drop a file.
Moreover the placeholder text can be translated (T function) and with javascript disabled the original control is rendered.

![immagine22](https://f.cloud.github.com/assets/3496662/795090/6a76b774-ecdb-11e2-90d5-1a925e141d91.jpg)