Config option to tell Tor whether it can use the network
Motivation 1: Tails wants to start Tor at boot, but have it not touch the network until the user has decided (e.g. via Vidalia) whether to use bridges.
Motivation 2: Tor-on-Android drains its battery when Tor tries to make circuits over and over. Sometimes there is no network, and Tor continues to try to make circuits. Orbot is able to learn whether there is a network, so it could tell Tor whether to avoid draining its battery.
We should add a config option so controllers can tell Tor when the network is gone/present, and Tor should stop doing network stuff in the 'gone' state. Another way of looking at this is an "airplane mode" for Tor.
I'm putting as an 0.2.3 milestone so I don't have to put it in 'unspecified'. I hope somebody will step up and volunteer it; but it can slip if not.