make Device interface

cli/grpc_test.go

cli/subscribe.go

controller.go

go.mod

go.sum

initialise_test.go

northbound/server/pnd.go

northbound/server/pnd_test.go

nucleus/device.go

nucleus/device_test.go

nucleus/initialise_test.go

nucleus/principalNetworkDomain.go

nucleus/principalNetworkDomain_test.go

nucleus/store.go

nucleus/store_test.go