Uses a proxy authenticator to set user and password in case of system pa...

...rams or else uses the original authenticator.

** DO NOT MERGE THIS **
Since I haven't been able to set up a test environment for this yet it is untested code in such that I don't know if it works with a proper proxy server. Please review the code to see what you think and meanwhile I'll continue trying to convince Windows about how a proxy server should be configured...