Add targets and rename stack -> base image where appropriate

[natalieparellano]

This is still a work in progress (and would require updating some docs tutorials) but may be an improvement over the current "hello world" samples.

I can pull this apart into 2 separate PRs if that would make it easier to review

Note: this branches off of other features with open PRs, so review and merge those first!

[natalieparellano]

Closing in favor of other PR