Update docs to use designated tfstate dir?

[vdice]

Currently the quick-start uses Terraform's default behavior and places the tfstate file in the working directoy (aws/terraform).

However, the user may change directories over the course of deploying their app(s). If/when they attempt to modify the state (via a terraform command) and are no longer in the directory where the state lives, there will be confusion and issues :)

Perhaps we should look at updating the terraform commands to supply -state=path (maybe path can be represented by an env var), so that the commands are pwd-agnostic.

[vdice]

The -state=path approach appears to be deprecated (see https://www.terraform.io/language/settings/backends/local) in favor of local backend config at the top-level of a Terraform project (eg terraform { backend "local" { path = "" } } }). Users will need to cd back to the main project directory (aws/terraform) when running terraform commands anyways, so I vote we relegate this to the domani of the user and their preferred terraform workflow.