Return environment/files when showing template for stack

Now we can use template-show to get the template of a specified stack, the template such as:
"heat_template_version": "2013-05-23",
    "resources": {
      "my_resource_group": {
        "type": "OS::Heat::ResourceGroup",
        "properties": {
          "resource_def": {
            "type": "OS::Nova::Server",
            "properties": {
              "flavor": 1,
              "image": {
                "get_param": "image"
              }
            }
          }
        }
      }
    },
    "parameters": {
      "image": {
        "type": "string"
      }
    }
In some cases, user also want to know the environment(such as user parameters) and files to clone stacks, but can't get these from the template only, so will be good to support return the environment and files information to users
I think we can add a request parameter 'with_env' and 'with_files' for template-show api.