consensus param for min bw to get Fast flag
To allow simpler network-wide testing, we should have a consensus param that, if set, instructs directory authorities to not give the Fast flag to relays with capacity less than that value.
Once enough directory authorities look at it, we can then start to experimentally verify answers to questions like "what happens to torperf results when we cut out all the relays under 50KB/s?"
In parallel to waiting for directory authorities to upgrade, I hope to get simulation answers to these questions.
One issue we need to ponder is: do we look at descriptor capacity or measured capacity?