Author: Shamim Rezaie
MDL-68076 core: new admin settings related to user feedback
http://git.moodle.org/gw?p=moodle.git;a=commit;h=2cbe9eaf42e4080c816d32590af2b6d695dfc22b
http://github.com/moodle/moodle/commit/2cbe9eaf42e4080c816d32590af2b6d695dfc22b
+ 3.9 en [enableuserfeedback,core_admin]
+ 3.9 en [enableuserfeedback_desc,core_admin]
+ 3.9 en [feedbacksettings,core_admin]
+ 3.9 en [userfeedbackafterupgrade,core_admin]
+ 3.9 en [userfeedbacknextreminder,core_admin]
+ 3.9 en [userfeedbacknextreminder_desc,core_admin]
+ 3.9 en [userfeedbackperiodically,core_admin]
+ 3.9 en [userfeedbackremindafter,core_admin]
+ 3.9 en [userfeedbackremindafter_desc,core_admin]