Updates to Azure SSH key references.

[yieter]

The generated SSH key pair was expected to be in JSON format, but the key pairs are not currently supplied by Terraform in that format. Perhaps they used to be? This fix removing the JSON decoding. Updates have been made both in the documentation/AzureTerraform.md file and in the Templates/Azure/Terraform/ssh.tf file since the relevant Terraform code appears in both places.

With a properly authenticated Azure CLI client, terraform init and terraform apply succeed when run in the Templates/Azure/Terraform directory.