Added global error handling; Added add/rename/delete group functionalities

gms-ui/package-lock.json

gms-ui/package.json

gms-ui/src/App.vue

gms-ui/src/api/server/index.js

gms-ui/src/components/GroupsPanel.vue

gms-ui/src/components/Main.vue

gms-ui/src/components/modals/ConfirmDeleteGroupModal.vue

gms-ui/src/components/modals/NewGroupModal.vue

gms-ui/src/components/modals/RenameGroupModal.vue

gms-ui/src/plugins/bootstrap-vue.js

gms-ui/src/store.js

gms/src/main/java/it/inaf/ia2/gms/authn/SecurityConfig.java

...ain/java/it/inaf/ia2/gms/controller/GroupsController.java

...n/java/it/inaf/ia2/gms/exception/BadRequestException.java

...java/it/inaf/ia2/gms/exception/UnauthorizedException.java

...src/main/java/it/inaf/ia2/gms/model/BaseModelRequest.java

...c/main/java/it/inaf/ia2/gms/model/CreateGroupRequest.java

gms/src/main/java/it/inaf/ia2/gms/model/GroupNode.java

...c/main/java/it/inaf/ia2/gms/model/GroupsModelRequest.java

...ain/java/it/inaf/ia2/gms/model/PaginatedModelRequest.java