Add a --disable-proxy option for disabling the proxy server.
Add a --disable-proxy option for disabling the proxy server.

A common problem people hit is that they end up going through a proxy
server when they don't want to. This change adds a --disable-proxy
option (DISABLE_PROXY in .reviewboardrc) that disables the HTTP(S) proxy
support.

clach04/rbtools_0.4.1,davidt/rbtools,halvorlu/rbtools,beol/rbtools,reviewboard/rbtools,davidt/rbtools,datjwu/rbtools,Khan/rbtools,1tush/rbtools,Khan/rbtools,haosdent/rbtools,halvorlu/rbtools,datjwu/rbtools,halvorlu/rbtools,davidt/rbtools,clach04/rbtools,haosdent/rbtools,reviewboard/rbtools,beol/rbtools,haosdent/rbtools,reviewboard/rbtools,datjwu/rbtools,bcelary/rbtools,beol/rbtools