A resource for defining a stack within a template.

The only way to reference nested stacks within a template is currently via a url as a provider template, this has the following problems:

1). Template shareability is limited because the template is segmented into multiple pieces across the internet.
2). Debugging parts of a template can become difficult when it is spread across multiple files.
3). ResourceGroup and AutoScalingGroup use provider templates to spin up groups of different resources, which become cumbersome to use when they are required to be defined in separate files.
4). Parameters often have to be duplicated in both the parent template and the provider template

A good solution to this problem would be to create a resource that defines a stack inline, allowing for multiple resources to be used within the "Group" resources.