Add/update Dockerfile templates from Draft
Draft has some packs to handle several languages. They're not particularly sophisticated, but there are some languages that we don't have templates for, such as Swift. We should take a look at https://github.com/Azure/draft/tree/master/packs and see if it's worth adding any missing languages and double-checking the languages we have.
We should continue to use expanded Dockerfiles rather than using
onbuild base images.