added missed throws tags in phpdoc for methods

This is a commit to make PhpStorm happy. It claims about missed throws tags in some method of this class. 

Also deleted the `@example` tag at the beginning, cause i can't see that file anywhere. Let me know if it should be kept there.
@andrerom well, dunno. i think what PhpStorm find in every case is line like https://github.com/ezsystems/ezpublish-kernel/blob/master/eZ/Publish/Core/Repository/ContentTypeService.php#L174
as far i see, rollback is produced as you say, but in this case an exception is thrown too, isn't it?

I think this is why PhpStorm claims about. 

Anyway, feel free to close this if is not ok.