Rework vagrant cluster set up.

* Have a single config file that mirrors other cluster providers
* Warn users not to use 'vagrant up' directly
* Allow 'extra' parameters to the docker daemon.  Fixes #2685
* Renumbers things so that they are more sane.  Master/minions are 10.245.1.x, container subnets are 10.256.x.1/24, portal is 10.247.0.0/16
Let's switch to `kubernetes/serve_hostname` -- we use that as a simple HTTP server in our e2e tests.