Refactor Docker startup scripts

[williamjallen]

Our Docker installation process was originally designed for testing and development purposes. With Kubernetes and other container-based deployment mechanisms becoming widespread, our Docker setup scripts are in need of a refactor to make them deployment-quality.

Amongst a slew of general refactoring work, I made the following notable changes:

• Apache is run under the current user by default, in case that user is not www-data. This is particularly useful for Kubernetes deployments, where the container is run under a random user.
• The Dockerfile has been moved to the root level of the repository and renamed to Dockerfile in accordance with traditional Docker naming conventions.
• APP_KEY is no longer generated by default. Users must specify it manually, and the container with fail to start with a message showing a random key if the APP_KEY environment variable is not set. Automatically generating keys as was done before is a bad idea, because the key (and thus, any data encrypted with it), will be lost if the container is restarted for any reason.
• A root user is no longer created by default. This is particularly useful for systems using OAuth or SAML, which should have all users provided via the 3rd party authentication provider.
• Legacy configurations will no longer be migrated automatically, since the migration will be lost if the container is restarted. If CDash administrators wish to run the migration manually, they may do so by running php artisan config:migrate.

I plan to make another PR to overhaul the Dockerfile and switch to php-fpm sometime soon.

[bstrdsmkr]

@williamjallen we recently deployed CDash in k8s and this would have made our lives easier, so thanks for the work!

I wanted to share a couple of other comments from our experience that could make things even easier

[josephsnyder]

@williamjallen, I'm having some trouble wrapping my mind around stopping the admin user creation. If a development environment runs the install step for us, we don't see the install page to set an account as an admin. One can get all the way to the login, and register a normal user, but then cannot create any projects.

Can we update the docker documentation to point out the user:save command that is available with exec cdash bash to create the admin account?

[williamjallen]

Good idea. I'll add a note to the docs.

The install page is of limited use for bare-metal systems, and is almost entirely useless for container-based systems. Using environment variables is by far the preferred way to go about setting configuration settings. I'll add a note to the docs in case anyone happens to be interested in manually creating a user for whatever reason.

[josephsnyder]

Needs a rebase for a conflict but otherwise LGTM!