fix #2517

app/views/contents/courseware/courseware_manager.php

app/views/course/courseware/manager.php

resources/assets/javascripts/bootstrap/courseware.js

resources/assets/stylesheets/scss/courseware.scss

...ces/vue/components/courseware/CoursewareCourseManager.vue

...rces/vue/components/courseware/CoursewareManagerBlock.vue

.../vue/components/courseware/CoursewareManagerContainer.vue

...e/components/courseware/CoursewareManagerCopySelector.vue

...es/vue/components/courseware/CoursewareManagerElement.vue

...ue/components/courseware/CoursewareManagerElementItem.vue

...ces/vue/components/courseware/CoursewareManagerFiling.vue

...ces/vue/components/courseware/CoursewareManagerImport.vue

...e/components/courseware/CoursewareManagerLinkSelector.vue

...omponents/courseware/CoursewareManagerTaskDistributor.vue

resources/vue/components/courseware/CoursewareOblong.vue

resources/vue/components/courseware/ManagerApp.vue

resources/vue/courseware-manager-app.js

resources/vue/store/courseware/courseware.module.js

resources/vue/store/courseware/structure.module.js