Pass basic auth settings in baseURL to xmlrpc lib

[aharter]

I also took the liberty to replace the legacy url.parse with the nodejs URL class.
This may or may not be a breaking change, since url.parse only throws a TypeError if the given URL is not a string. The URL class throws the error, if the input is not a valid URL.

See https://nodejs.org/api/url.html#url_new_url_input_base
and https://nodejs.org/api/url.html#url_url_parse_urlstring_parsequerystring_slashesdenotehost

[vettloffah]

Thanks for the PR - can you help me understand the basic auth feature. Why do we want / need it with the username and password params already included?

[aharter]

We have test instances exposed to the internet, which we protect from unwanted access using basic auth on the load balancer level.
First, I thought about adding the possibility to pass all client options available to the underlying xmlrpc (headers and cookies) to allow maximum flexibility. However, I opted for just the basic auth to keep it simple.

[vettloffah]

This has been published in version 3.2.0. Thank you!