Store terraform-related files in local directory

[ageorgou]

At the moment, the files (.tf and .tfstate) that Terraform creates are put into a temporary directory, which is deleted after deployment. It would be good to store these so they can be examined if required. This would also eliminate the need to do terraform init every time, and would simplify destroying a host (#43). The file name, which can reuse the unique name scheme when available (#50), can then be stored in the database instead of its contents.

Note that terraform apply can take a state argument, to save the state in a non-default path (https://www.terraform.io/docs/commands/apply.html)

• [ ] Change deployer to use the "persistent" directory instead of TemporaryDirectory.
• [ ] Update commands when deploying (remove call to init, ... ).
• [ ] Change set-up instructions to include the creation of a local directory and an initial run of terraform init in it.
• [ ] Can we check whether terraform init has been run already? If the directory already has contents from previous deployments and we rerun init, it will try to refresh their states which could take a long time. At least add a note about this in the set-up instructions.
• [ ] Add a refresh function (definitely in the code, possibly in the GUI) to update the state of a deployed host.

[ageorgou]

A better alternative might be to use Terraform's remote state feature with Azure (some info here and here). It seems that Terraform will then access the files as and when needed automatically. To view the files ourselves, we can use Azure Storage Explorer.