The docker RUN uses /bin/sh as the default, this does not support curly braces. aura#308

Closes: #184

/app/site_media is mapped to a named volume when deploying with docker compose as part of AURA Playout. Docker creates the directory as root where a named volume should be mapped to if it does not already exist. We therefore create the mount point in advance and set permissions in order to give the aura(app) user access. #184

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.