Proposal: remove features

[munkyboy]

After seeing how elsy has been used for a couple of years now, I think we should simplify it.

• remove templates. They are hidden and feel like magic. Also hard to maintain WRT the docker-composeversion declaration
• remove self-updating. This is brittle and unused. This task should be handled by a package manager. If anything, we should replace it with a system that occasionally reminds the user if a new version is available.
• remove project-name option. We should promote using the standard COMPOSE_PROJECT_NAME env var.

I would like to bundle these changes into the next major version.

[munkyboy]

adding to the list...

• require opt-in to build a docker image. Currently, elsy checks if a Dockerfile is present, then enters the docker build routine. However, it requires that the docker-image-name option be present. Instead, we should only enter the docker build routine if the docker-image-name option is present.

I ran into this when I created a repo with a ./Dockerfile but did not want an image built