Author: Andrew Hancox
MDL-51687 mod_folder: Trigger event when downloading all files.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=23b6636997b3a9e3000cce6cec2637d80654950e
http://github.com/moodle/moodle/commit/23b6636997b3a9e3000cce6cec2637d80654950e
+ 3.1 en [eventallfilesdownloaded,mod_folder]