Refactor store interfaces and provide database as example implementation

cli/cmd/deviceList.go

cli/cmd/init.go

controller/api/initialise_test.go

controller/config/config.go

controller/config/config_test.go

controller/config/config_test.toml

controller/controller.go

controller/interfaces/device/device.go

controller/interfaces/device/deviceStore.go

controller/interfaces/networkdomain/pnd.go

controller/interfaces/networkdomain/pndStore.go

controller/interfaces/southbound/sbi.go

controller/interfaces/southbound/sbiStore.go

controller/mocks/Change.go

controller/mocks/Device.go

controller/mocks/NetworkDomain.go

controller/mocks/Plugin.go

controller/mocks/SouthboundInterface.go

controller/mocks/Storable.go

controller/mocks/Store.go