Adapt Tor installer to allow users to avoid connecting to the public tor network

We need a way to avoid touching the public network for deb/rpm users, in a way that doesn't clutter the installer, scare users, and/or subject users to warning fatigue.

It has been done for Vidalia already,

• #2905 (closed) "Adapt Vidalia UI to allow users to avoid connecting to the public tor network"
• https://trac.torproject.org/projects/tor/attachment/ticket/2905/xxx-no-public-network.txt

What about the Tor installer?