Extract CodeStar project Cfn template and check into source control?

[mathomas]

... with changes to support custom policies and container versions needed. Apply the changes to the running CodeStar Cfn stack.

This might be a better way (even though it's a bit weird and chicken/egg-ey) to manage some of the changes I (Mike) have had to make in the console over the course of the project, as we've done more sophisticated things:

• change the CodeBuild container to Node 8.x
• add additional policies to the CodeStarWorker-buildit-slink-CloudFormation role as we pulled in more services.

That said, it might be a bit risky checking in the Cfn template. I think we should make it clear that the Cfn template likely only applies to this particular instance of our CodeStar project -- if someone fires up a brand new one, it may not be wise for them to just apply the checked-in Cfn template to their new project.

So, an alternative might be a couple of CLI scripts to add the role policies and update the CodeBuild step to use the correct Node version.