Refactoring and cleanup

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

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

...n/java/it/inaf/ia2/gms/controller/HomePageController.java

...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

...n/java/it/inaf/ia2/gms/model/request/AddGroupRequest.java

.../java/it/inaf/ia2/gms/model/request/AddMemberRequest.java

...ava/it/inaf/ia2/gms/model/request/AddMemberWsRequest.java

...a/it/inaf/ia2/gms/model/request/AddPermissionRequest.java

...it/inaf/ia2/gms/model/request/AddPermissionWsRequest.java

...ain/java/it/inaf/ia2/gms/model/request/MemberRequest.java

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

...va/it/inaf/ia2/gms/model/request/RemoveMemberRequest.java

...ava/it/inaf/ia2/gms/model/request/RenameGroupRequest.java

...c/main/java/it/inaf/ia2/gms/model/request/TabRequest.java

...ava/it/inaf/ia2/gms/model/response/BaseModelResponse.java

...ava/it/inaf/ia2/gms/model/response/GroupsTabResponse.java

...java/it/inaf/ia2/gms/model/response/HomePageResponse.java

...in/java/it/inaf/ia2/gms/model/response/PaginatedData.java