[BUG] Phalcon\Http\Request::hasFiles() does not work with file arrays

See #884 — this fixes it.

However, for #878: what should the key be in case of a file array? That is, if we have something like

```html
<p>file1:<input type="file" name="photo[]"></p>
<p>file2:<input type="file" name="photo[]"></p>
<p>file3:<input type="file" name="photo[][]"></p>
<p>file4:<input type="file" name="photo[][]"></p>
<p>file5:<input type="file" name="photo[][][]"></p>
<p>file6:<input type="file" name="photo[][][][][]"></p>
```
:question: