Added modal and completed API for members/permissions removal

...client/gms-cli/src/main/java/it/inaf/ia2/gms/cli/CLI.java

...t-lib/src/main/java/it/inaf/ia2/gms/client/GmsClient.java

...b/src/test/java/it/inaf/ia2/gms/client/GmsClientTest.java

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

gms-ui/src/components/GroupsPanel.vue

gms-ui/src/components/Main.vue

gms-ui/src/components/MembersPanel.vue

gms-ui/src/components/PermissionsPanel.vue

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

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

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

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

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

...ui/src/components/modals/ConfirmRemovePermissionModal.vue

gms-ui/src/store.js

...in/java/it/inaf/ia2/gms/controller/MembersController.java

...ava/it/inaf/ia2/gms/controller/PermissionsController.java

...java/it/inaf/ia2/gms/controller/WebServiceController.java

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

...main/java/it/inaf/ia2/gms/model/AddPermissionRequest.java