Provide native implementation of AWS pseudo parameters

Pseudo Parameters are parameters that are predefined by AWS CloudFormation. You do not declare them in your template. Use them the same way as you would a parameter, as the argument for the Ref function.

Currently we use these pseudo parameters with all the templates including HOT and when using only Heat native resources (Independent of AWS. e.g. using OS::Nova::Server) . We should provide native implementation of AWS pseudo parameters so that we can reference them while using heat native resources.

Currently, it looks like following, as an example,

1. Create a stack using heat native only template (e.g. ../hot/F18/WordPress_Native.yaml or ..hot/F18/NovaInstanceWithCinderVolume_Native.yaml)
2. Run "stack-show". Part of the out is below,
| parameters | { |
| | "instance_type": "m1.small", |
| | "key_name": "heat_key", |
| | "availability_zone": "nova", |
| | "AWS::StackId": "arn:openstack:heat::85e5c894ba43425e854695b25b854b6a:stacks/hello/1aca913a-24fa-4696-998c-674b365a87e7", |
| | "image_id": "F18-x86_64-cfntools", |
| | "AWS::StackName": "hello", |
| | "AWS::Region": "ap-southeast-1", |
| | "volume_size": "1"

For more information on AWS Pseudo Parameters, refer to:
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/pseudo-parameter-reference.html