lncli: add loadmc command

This command lets one import data exported by `lncli querymc > mc.json`
via `lncli loadmc --mcdatapath mc.json`.

cmd/commands/routerrpc.go

@@ -7,6 +7,7 @@ func routerCommands() []cli.Command {
 	return []cli.Command{
 		queryMissionControlCommand,
 		importMissionControlCommand,
+		loadMissionControlCommand,
 		queryProbCommand,
 		resetMissionControlCommand,
 		buildRouteCommand,