Clean up Vagrant/Chef configs

Vagrant and Chef should now mostly just work. This commit adds a key
generation script to make cert management a little easier. It also
adds a lot more Vagrant documentation.
Move our cookbooks around.

Rename cookbooks from *-main to oe-*.
Give Vagrant VMs unique names.

VirtualBox complains if you try to reuse VM names, which is bad when
custom sites try to use Vagrant. This commit appends a unique suffix to
each VM name. Sites may want to use a more human readable suffix
instead, e.g. db-demo instead of db-af34c9ee73.