Adding Sidecar Container for configs and checks

The primary addition of this release is to add a sidecar container that can be used to add configs and health checks to the primary consul container, with the end goal of being able to update and use the upstream Consul container distributed by Hashicorp. The default sidecar is fitnesskeeper/consul-healthchecks:latest but this can be swapped out for another container image. In addition, the ECS Task definition has been updated to make it more compatible with the new versions of the terraform-aws-provider.