Convert Terraform working directories to a Terraform module

[nnutter]

It would be nicer if these were implemented as Terraform modules so they could be integrated into existing Terraform working directories. I've done so in a private fork for the per-project case and it was not very complex. Obviously, it might be more complex for the other working directories and then there's the matter of updating Google's docs, etc. so I'm not saying it'd be trivial; something to think about.