Handled tar/zip creation and download of resulting file

...ain/java/it/inaf/ia2/vospace/ui/VOSpaceUiApplication.java

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

...it/inaf/ia2/vospace/ui/controller/DownloadController.java

...java/it/inaf/ia2/vospace/ui/controller/JobController.java

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

...ackend/src/main/java/it/inaf/ia2/vospace/ui/data/Job.java

...naf/ia2/vospace/ui/controller/DownloadControllerTest.java

.../it/inaf/ia2/vospace/ui/controller/JobControllerTest.java

...t/inaf/ia2/vospace/ui/controller/NodesControllerTest.java

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

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

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

...-ui-frontend/src/components/modal/ConfirmArchiveModal.vue

vospace-ui-frontend/src/store.js