Add current state identifiers to Read/Delete invocation

There are scenarios where the primary identifier is created by the resource provider itself. For those situations, you need to check another information from the current state (e.g. a name attribute) because usually the underlying AWS API does not know anything about the primary ID.

So I propose that the previous state property be filled with the current state by the upstream service, otherwise there is no real way to retrieve the state stored in CloudFormation during read.

You can find a little bit more context here: https://github.com/org-formation/aws-resource-providers/issues/26