Author: Sara Arjona
MDL-79918 format: Improve the Hidden sections setting
http://git.moodle.org/gw?p=moodle.git;a=commit;h=464447c883f0f8137006b0a96f987190a860b9b0
http://github.com/moodle/moodle/commit/464447c883f0f8137006b0a96f987190a860b9b0
+ 5.1 en [hiddensectionscollapsed,core]
+ 5.1 en [hiddensectionscollapsed_description,core]
+ 5.1 en [hiddensectionsinvisible,core]
+ 5.1 en [hiddensectionsinvisible_description,core]