Review docs

[florianm]

Once the docker-compose deployment is in production for both build and build2xlsform, I'd love to review and update the docs in this repo.

If this were entirely up to me, I'd suggest:

• Drop offline branch and replace with instructions to run docker-compose locally.
• Drop ansible branch in favour of deployment through docker-compose.
• Remove references to deprecated branches and deployments from docs and code.
• Reduce overlap in docs:
  • architecture.md: Explanations of how Build works.
    • navigating code
    • dependencies
    • server side and database
    • deployment options (source, docker-compose)
  • contributing.md: Explanations of how to work on Build.
    • code of conduct, communication and collaboration with core team
    • development process (build and run code locally, common pitfalls)
    • local testing (build and run Docker images locally)
    • deployment process
    • migration pathway for production database (pg_dump into local folder, bind mount, pg_restore into docker service's db)
    • maintenance: how to run management commands against the running odkbuild container, e.g. update a user's password from the Ruby shell irb
  • README.md: shorten to refer to above docs.
• Include a release issue template with a checklist for the release process

[florianm]

Status quo:

• https://build.getodk.org/ runs build 0.4.2 with build2xlsform 1.9 - release "source install, docker ready".
• https://staging.build.getodk.org/ runs build 0.4.1 with build2xlsform 1.9.

Next steps:

• Deploy build 0.4.2 with build2xlsform 1.9 to staging (source install)
• Change staging to docker-compose and migrate db using transfer bind mount
• Update docs with docker-compose as main deployment process