Use a better default torrc

There should really be a function added to Tor to use a better default torrc, depending on what you'd like to use it for. Even if it's just a one-time torrc creation/replacement function (with no editing of one that's in place), I think it would be an improvement over what exists now (which assumes client-only).

Example: tor --torrc -r --max=4mbps --burst=6mbps for running a relay that advertises 4mbps speed, with a burst of 6mbps. Or: tor --torrc -b --obfs3 for creating a bridge of the obfs3 variety.