reduce lib installed, collect static during build

  * keep app and test related libs but remove sphinx and django-extensions related dependencies.
  * remove apache2-dev
  * collect static, and get ready to copy it on startup if needed to be serve by another container
  * gunicorn only reload when used in docker-compose
  * none root user
  * run migration on startup
  * copy static files to $STATIC_ROOT_ON_STARTUP_COPY when mounted