add support to pass a json as arg for js-script

[pepoviola]

Add support for passing a json as arg to js-script. Should be single quoted json like:

alice: js-script ./0001-custom-json.js with '{"account": "alice", "nums": [0,1,2,3], "bool": true}' within 200 seconds

And in the script you have access to the Object directly

async function run(nodeName, networkInfo, argObject) {
    if (argObject.account != "alice") {
        console.log("JSON err: field name");
    }

cc: @bkontur