Implemented remaining createdBy, fixed #135

...src/main/java/at/tuwien/endpoints/IdentifierEndpoint.java

...ce/rest-service/src/test/java/at/tuwien/BaseUnitTest.java

...a/at/tuwien/service/IdentifierServiceIntegrationTest.java

...est/java/at/tuwien/service/IdentifierServiceUnitTest.java

.../main/java/at/tuwien/exception/UserNotFoundException.java

...rc/main/java/at/tuwien/repository/jpa/UserRepository.java

...es/src/main/java/at/tuwien/service/IdentifierService.java

...services/src/main/java/at/tuwien/service/UserService.java

...in/java/at/tuwien/service/impl/IdentifierServiceImpl.java

...src/main/java/at/tuwien/service/impl/UserServiceImpl.java

...i/src/main/java/at/tuwien/api/container/ContainerDto.java

...api/src/main/java/at/tuwien/api/database/DatabaseDto.java

.../src/main/java/at/tuwien/api/database/table/TableDto.java

.../java/at/tuwien/api/database/table/columns/ColumnDto.java

...pi/src/main/java/at/tuwien/api/identifier/CreatorDto.java

...src/main/java/at/tuwien/api/identifier/IdentifierDto.java

.../api/src/main/java/at/tuwien/api/user/UserDetailsDto.java

...data-db/api/src/main/java/at/tuwien/api/user/UserDto.java

...t/tuwien/entities/database/table/columns/TableColumn.java

...rvice/src/main/java/at/tuwien/endpoint/QueryEndpoint.java