allow to pass meta as JSON string

[AndreMaz]

Fixes #69

Allows to pass meta as JSON encoded as string. For more info check the updates in unit test.

Also, adds an additional check that validates the nodeID in dcall command

    if (
        nodeID &&
        !broker.registry
            .getServiceList({})
            .map((service) => service.nodeID)
            .includes(nodeID)
    ) {
        console.error(
            kleur.red().bold(`>> Node '${nodeID}' is not available.`)
        );
        return;
    }

Examples: