Use 'local' backend for Terraform modules by default

[glennmusa]

Benefit/Result/Outcome

A user could deploy Terraform from the repo without setting up dependencies.

In a future where MLZ doesn't provide BASH scripting to stand-up a Storage Account and Container for storing Terraform state, a local backend would instead allow the Terraform modules to be deployed independently.

Description

https://www.terraform.io/docs/language/settings/backends/local.html

Acceptance Criteria

• Set the Terraform modules to local backend (and allowing the default path to be used)
• Document (point to documentation) on how to use different backends
• Document (point to documentation) on how to use the azurerm backend

[brooke-hamilton]

Related to #354