refactoring for initialism linting errors

mocks/PrincipalNetworkDomain.go

mocks/SouthboundInterface.go

mocks/Storable.go

nucleus/controller.go

nucleus/device.go

nucleus/device_test.go

nucleus/http.go

nucleus/http_test.go

nucleus/principalNetworkDomain.go

nucleus/principalNetworkDomain_test.go

nucleus/southbound.go

nucleus/southbound_test.go

nucleus/store.go

nucleus/store_test.go