MDL-54751 core_course: Edit course libs to support deletion flag

Changed the course libs such that module and section deletion is now
handed off to relevant functions in the util class and exempted
modules scheduled for deletion from the course backups.

course/editsection.php

@@ -50,7 +50,7 @@ if ($deletesection) {
     if (course_can_delete_section($course, $sectioninfo)) {
         $confirm = optional_param('confirm', false, PARAM_BOOL) && confirm_sesskey();
         if ($confirm) {
-            course_delete_section($course, $sectioninfo, true);
+            course_delete_section($course, $sectioninfo, true, true);
             $courseurl = course_get_url($course, 0, array('sr' => $sectionreturn));
             redirect($courseurl);
         } else {