aura#251

Close: #164

- replace `run.sh init-db` script with `initialize` Makefile target,
- run `migrate` and `loadfixtures` as prerequisites to `initialize` target,
- add `run.dev`, `run.debug` and `run.prod` targets,
- add `migrate` as prerequisite for run targets.

Update Dockerfile accordingly

Closes #127

- Run as aura with AURA_UID
- Use WORKDIR /app
- Install Poetry in /opt/poetry

This should be enough for now

This reverts commit c8dd9233.