Enhancement: optional input and use of proxy credentials

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Set up behind an authenticating proxy(typical corporate config)
2. Attempt to up-or-download a site

What is the expected output? What do you see instead?
Expected: site transfers
Actual: Authentication error - due to firewall not allowing traffic

What version of the product are you using? On what operating system?
1.04 on Windows XP

Please provide any additional information below.

Original issue reported on code.google.com by rdmast...@gmail.com on 24 May 2012 at 7:43