GitLab

- Added local data directory for MySQL (`db/storage`) to ensure data
  persistency.
- Removed `make_compose_containers_local.sh` and added `build` entries
  in `docker-compose.yml`.
- Forwarded port 31215 on the backend container for TCP access.
- Forwarded port 31216 on the stats container for websockets.
- Forwarded port 80 on the frontend to 31280 to avoid conflicts.
- Shared `cloogle.log` between backend and stats.
- Bumped PHP version to 7.0 in frontend.
- Rollback change in `frontend/stats/client.js` that made the live
  statistics only available from local hosts.
- Moved `frontend/conf.php.example` to `frontend/conf.php`, because this
  is no longer secret.
- Removed comment in `frontend/api.php`.
- Removed outdated setup instructions in `README.md`.