Adding persistence to gobs-of-machines

A couple updates on the gobs-of-machines work from a while back! The smaller update of the two: I've renamed what I was calling "provisioners" to "providers". This is a bit of an attempt to align my terminology with that of other tools like Terraform . Ultimately when deploying real instances I'll need something to install/configure the hob-server component on the new machine, and it might make…