Add xml2json func, expandReference parseXML(body)

[mtuchi]

Short Description

Add xml2json function and improve parseXML function

Why ?

The implementation team has ongoing project in partnership with vera team. This project will have an automated workflow that will take data from SunSystem which has a SOAP API to Salesforce. To make the transformation process easy, We need an adaptor function that can be used to convert the xml response to a json object.

Implementation Notes #446

Add xml2json(xmlString, options, callback) function that uses xml2js package. This function will take xml string and convert it to json object.

This PR also contain improvements for parseXML function. The first argument of the parseXML function was not using expandReferences which makes it hard to access data from state in job code.

Review Checklist

• Does the PR do what it claims to do?
• Are there any unit tests? Should there be?
• Is there a changeset associated with this PR? Should there be? Note that
  dev only changes don't need a changeset.

[mtuchi]

Adding xml2json in http is not advised for the time being since parseXML is already useful enough.