Implemented delete node modal dialog and calls

...ain/java/it/inaf/ia2/vospace/ui/client/VOSpaceClient.java

...va/it/inaf/ia2/vospace/ui/controller/NodesController.java

...ain/java/it/inaf/ia2/vospace/ui/service/NodesService.java

vospace-ui-frontend/src/api/mock/data/nodes/folder1.html

vospace-ui-frontend/src/api/mock/data/nodes/folder2.html

vospace-ui-frontend/src/api/mock/data/nodes/root.html

vospace-ui-frontend/src/api/mock/index.js

vospace-ui-frontend/src/api/server/index.js

vospace-ui-frontend/src/assets/css/fonts.css

vospace-ui-frontend/src/components/Main.vue

...e-ui-frontend/src/components/modal/ConfirmDeleteModal.vue

vospace-ui-frontend/src/main.js

vospace-ui-frontend/src/store.js