phd2 update should allow user to specify network proxy settings

[agalasso]

phd2 update should still work in case user is behind an HTTP proxy and we provide the user with a way to specify the proxy settings

[agalasso]

as a workaround see https://stackoverflow.com/questions/9445489/performing-http-requests-with-curl-using-proxy:

For example: launch phd2 via a cmd file, phd2.cmd:

@echo off
https_proxy=https://username:password@proxy-host:port
phd2.exe