Introduce HTTP authentication options to Script items and Webhooks

Currently, there is no HTTP authentication configuration possible from Script items and Webhooks. For simpler systems, it requires to use Basic auth header, but for systems that require NTLM or other auth types, it becomes a problem.

HTTP authentication configuration is available in libcurl and is provided as an option in Web scenarios and HTTP agents. It seems that this functionality should be available in Script items and Webhooks as well.