[REQUEST] ECR image hook

[ITProKyle]

With the release of public ECR (in response to Docker Hub limits) and the ability to use ECR images as Lambda function deployment package ECR is now a very appealing option. There is a void in capabilities to build, test, and push images.

Acceptance Criteria

• build docker image
• optionally test the image leaving this out for now, until there is a need for it
• push the image that was built
• push image that has already been built
• delete image locally and/or from ECR
• provide access to sane docker options in the build/push process
• return information relevant to use as Lambda function deployment package and with other services

[ITProKyle]

After starting work on the hook, I noticed most of the logic I was writing was around docker and not ECR. So, this is now going to be implemented as a docker hook with features to simplify use with ECR.

[ITProKyle]

Looking into returning relevant info to use as a Lambda Function deployment package I noticed that CloudFormation documentation does not reflect supporting this yet while the release blog post stated that CloudFormation does support it.

Looking through the API docs, I was able to piece together a working CloudFormation template for testing. I also started a PR to add support to Troposphere (cloudtools/troposphere#1846).