Implemented file upload

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

...ava/it/inaf/ia2/vospace/ui/controller/BaseController.java

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

...a/it/inaf/ia2/vospace/ui/controller/UploadController.java

...ain/java/it/inaf/ia2/vospace/ui/data/UploadFilesData.java

...f/ia2/vospace/ui/exception/PermissionDeniedException.java

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

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

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

...ce-ui-frontend/src/components/modal/CreateFolderModal.vue

...ace-ui-frontend/src/components/modal/UploadFilesModal.vue

vospace-ui-frontend/src/store.js