2.2/ogv support

This has been plaguing me for quite some time and I finally got it figured out. The problem is with the fun mime type that gets tossed around for OGV.

Anyone here would say, "oh well ogv? that's a mime type of video/ogg! Everyone and their grandma knows that!". Well yeah, but it turns out the server is often wrong. I tried [using this page](http://wiki.xiph.org/index.php/MIME_Types_and_File_Extensions) to attempt to assign the correct mime type, but nothing was working.

This [stackoverflow answer](http://stackoverflow.com/a/10850763) helped me solve this issue. If you [go to this line](https://github.com/pyrocms/pyrocms/blob/2.2/master/system/codeigniter/libraries/Upload.php#L218) in the CodeIgniter uploads class, and change that line to the following:

```php
$this->_file_mime_type($_FILES[$field]); var_dump($this->file_type); die();
```

Then check your ajax response on the `upload` POST function if the files upload, you will see the `var_dump` of the *REAL* mime type that the server is returning. In this case it was returning `application/ogg`!

In summation, this mime type is needed to upload videos for Firefox, since they [cannot play mp4 due to licensing](https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats#MP4_H.264_(AAC_or_MP3)). Hopefully in the future everything will be [webm video](http://www.webmproject.org/).

**Sidenote**

I am using the default .htaccess. Modifying it and adding the mime type of `video/ogg` may mean you need to update the mimes.php file to reflect that change. But for now, this is what worked for me.