Add AutoProxyServer

This adds automatic proxy server configuration on Windows.

When EnableAutoProxy is set (default), instances of the WebClient class will receive the appropriate proxy server for their BaseUrl.

Retrieves IE settings, including auto-detect and auto-config scripts and applies according to the specified BaseUrl.

Closes #69
I would feel more comfortable if all of this was handled with a `On Error GoTo auto_ErrorHander` or `On Error GoTo auto_Cleanup` just in case that does the memory releasing and http close