Add stock images, closes #2482

...es/vue/components/courseware/CoursewareShelfDialogAdd.vue

...vue/components/courseware/CoursewareStructuralElement.vue

.../components/courseware/CoursewareUnitItemDialogLayout.vue

resources/vue/components/stock-images/ActionsWidget.vue

resources/vue/components/stock-images/AttributesFieldset.vue

resources/vue/components/stock-images/ColorFilterWidget.vue

resources/vue/components/stock-images/EditDialog.vue

resources/vue/components/stock-images/ImagesList.vue

resources/vue/components/stock-images/ImagesListItem.vue

resources/vue/components/stock-images/ImagesPagination.vue

resources/vue/components/stock-images/MetadataBox.vue

resources/vue/components/stock-images/NavigationWidget.vue

...s/vue/components/stock-images/OrientationFilterWidget.vue

resources/vue/components/stock-images/Page.vue

resources/vue/components/stock-images/SearchWidget.vue

...urces/vue/components/stock-images/SelectableImageCard.vue

resources/vue/components/stock-images/Selector.vue

resources/vue/components/stock-images/SelectorDialog.vue

resources/vue/components/stock-images/SelectorSearch.vue

resources/vue/components/stock-images/TagsInput.vue