Define ReducedExitPolicy/ExitPolicyGroups in tor/dirauths
We've got a lot of different relays running a lot of slightly different versions of https://trac.torproject.org/projects/tor/wiki/doc/ReducedExitPolicy. We should maintain one version either in the directory authority consensus, or directly in the tor source itself.
We may also want to split the thing into service groups, like the Vidalia UI does. It should be a part of tor though, not Vidalia, since most high capacity exits don't run with Vidalia.