Improve docker-compose & requirements.txt

First:

• I think you can remove SQLALCHEMY_TRACK_MODIFICATIONS from the docker-compose file.

Second:

• I would suggest that we add all the dependencies, that are installed in the docker-compose file additionally to the base requirements.txt explicitly to the requirements.txt file. I think packages like djangorestframework-jsonapi are important enough to be listed there (I mean the requirements.txt even contains the gunicorn package).