Given a CF template that defines outputs as named exports, I expect the "describe-stack" endpoint to include the exported names. With localstack, that is currently not the case.

Example template:
```yaml
  Outputs:
    VPCId:
      Value: {Ref: MyVPC}
      Export:
        Name: My-VPCId

  Resources:
    MyVPC:
      Properties:
        CidrBlock: 10.0.0.0/16
      Type: AWS::EC2::VPC

```

AWS:
```
$ aws cloudformation describe-stacks
...
                {
                    "OutputKey": "VPCId",
                    "OutputValue": "vpc-0123456789",
                    "ExportName": "My-VPCId"
                },

```

localstack:
```
$ aws cloudformation --endpoint-url=http://localhost:4581/ describe-stacks
...
                {
                    "OutputKey": "VPCId",
                    "OutputValue": "vpc-0123456789"
                },
...
```
sns_client = aws_stack.connect_to_service('sns')
    topics = sns_client.list_topics()
    for topic in topics['Topics']:
        topic_arn = topic['TopicArn']
        if topic_arn.endswith(':%s' % name):
            return topic_arn
def queue_url_exists(queue_url):
    sqs_client = aws_stack.connect_to_service('sqs')
    queues = sqs_client.list_queues()
    return queue_url in queues['QueueUrls']
def stream_exists(name):
    kinesis_client = aws_stack.connect_to_service('kinesis')
    streams = kinesis_client.list_streams()
    return name in streams['StreamNames']
def get_stack_details(stack_name):
    cloudformation = aws_stack.connect_to_service('cloudformation')
    stacks = cloudformation.describe_stacks(StackName=stack_name)
    for stack in stacks['Stacks']:
        if stack['StackName'] == stack_name:
            return stack
def describe_stack_resource(stack_name, resource_logical_id):