Instantiate a new Okta API Groups helper with the given API token
@param apiToken
@param domain
@param preview
@constructor
function OktaAPIGroups(apiToken, domain, preview)
{
    if(apiToken == undefined || domain == undefined) 
    {
        throw new Error("OktaAPI requires an API token and a domain");
    }
    this.domain = domain;
    if(preview == undefined) this.preview = false;
    else this.preview = preview;
    this.request = new NetworkAbstraction(apiToken, domain, preview);
    this.helpers = require('./OktaAPIGroupsHelpers.js')
}