Added web service controller logic and tests

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

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

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

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

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

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

gms/src/main/java/it/inaf/ia2/gms/persistence/GroupsDAO.java

...main/java/it/inaf/ia2/gms/persistence/MembershipsDAO.java

...main/java/it/inaf/ia2/gms/persistence/PermissionsDAO.java

...a/it/inaf/ia2/gms/persistence/model/MembershipEntity.java

...a/it/inaf/ia2/gms/persistence/model/PermissionEntity.java

gms/src/main/java/it/inaf/ia2/gms/service/GroupsService.java

...src/main/java/it/inaf/ia2/gms/service/MembersService.java

...main/java/it/inaf/ia2/gms/service/PermissionsService.java

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

...af/ia2/gms/service/PermissionsServiceIntegrationTest.java