Make the new "extra dormant" code configurable
I think we want at minimum these options:
A way to say how long without activity counts for becoming dormant.
A way to say whether having an open stream with no network traffic on it should keep Tor from becoming dormant.
I think maybe we also want:
A way to say how often to check for becoming dormant.
A way to say that Tor should start out dormant, or should remember dormancy status across invocations?