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"
                },
...
```
try:
            return _parse_and_create_resource(logical_id,
                resource_json, resources_map, region_name, update=True)
        except Exception as e:
            LOG.error('Unable to parse and update resource "%s": %s %s' %
                      (logical_id, e, traceback.format_exc()))
            raise
    def _parse_and_create_resource(logical_id, resource_json, resources_map, region_name,
            update=False, force_create=False):
        stack_name = resources_map.get('AWS::StackName')
        resource_hash_key = (stack_name, logical_id)
        
        updating = CURRENTLY_UPDATING_RESOURCES.get(resource_hash_key)
        LOG.debug('Currently processing stack resource %s/%s: %s' % (stack_name, logical_id, updating))
        if updating:
            return None
        
        resource_tuple = parsing.parse_resource(logical_id, resource_json, resources_map)
        if not resource_tuple:
            return None
        _, resource_json, _ = resource_tuple
        
        props = resource_json['Properties'] = resource_json.get('Properties') or {}
        if resource_json['Type'] == 'AWS::Lambda::EventSourceMapping' and not props.get('StartingPosition'):
            props['StartingPosition'] = 'LATEST'
        
        resource = resources_map._parsed_resources.get(logical_id)
        if resource and not update and not force_create:
            return resource