Extension with support for Lambda functions

[andrewdmay]

As this utility may be used with lambda functions where it's necessary to upload files to S3, possibly from a zip file previously created in a CI/CD pipeline, there may be value in building some of this functionality into stackmanager.

It may also be worth considering template alterations in the style of aws cloudformation package or sam package where a local file path can be converted into the S3 Bucket and Key after an automated upload. The template is being loaded into memory when creating a changeset, so it would be possible to manipulate it.

[andrewdmay]

The build-lambda and upload commands are a good start, but a single command that combines these and deploy (and potentially finds the code from the template to build and then manipulates it to put in the Bucket/Key like sam build/deploy) could make this more useful for running locally. Keeping this open for now.