Refactor SSM resources out of ecs-cluster.yaml

[MikeTheCanuck]

#66 resolves an SSM access issue that prevented ECS containers with any other role but our particular hacko-integration-ECSRole-us-west-2 from accessing the SSM parameters at all.

Once we've stabilized the cluster and confirmed it's deploying well, then we can refactor these hard-coded Resources out of ecs-cluster.yaml and into a master.yaml. This will enable this CloudFormation stack to be re-used in other environments where they could have a different KMS encryption key and/or SSM parameter namespaces.