* refactored and revamped the capacity threshold calculation to take

into account various skew situations and the capacity growth constant with
the intent of producing a higher quality threshold whenever possible
* increased the minimum # of fast peers from 4 to 8 (yay), which means we'll
try to have at least some peers to choose from
* added a new router config option - "router.maxParticipatingTunnels".  This is
useful for gracefully shutting down the router (aka set it to 0 and wait until
the router is no longer participating in tunnels, then shutdown).  You can
probably also come up with other situations where this is useful, but I don't
want to spoil all the fun ;)