Updated Version

The bug with the get methode was fixed. Unnecessary code were deleted. The function "if (has_capability('moodle/course:update',$context)) in comments.php was deleted because I think that the students should be write comments. I added the string media_notauth in lang/en/slideshow.php and in media.php.
Updated on moodle standard.
![caption](https://f.cloud.github.com/assets/3150458/50122/b7df3a44-5993-11e2-8c9f-a5eac7543e2d.png)
![comments](https://f.cloud.github.com/assets/3150458/50123/be692a78-5993-11e2-9ec2-3965020d40ad.png)
![media](https://f.cloud.github.com/assets/3150458/50124/bff0f6dc-5993-11e2-921d-c9a475feadce.png)