Author: David Knuplesch
MDL-60710 course: setting to show/hide duplicate coursecontact
http://git.moodle.org/gw?p=moodle.git;a=commit;h=a487a3edf2f20d75dfeb26f3c8516ed72f5f25d0
http://github.com/moodle/moodle/commit/a487a3edf2f20d75dfeb26f3c8516ed72f5f25d0
+ 3.6 en [coursecontactduplicates,core_admin]
+ 3.6 en [coursecontactduplicates_desc,core_admin]