Black-format the Python modules and add simple Make instructions

[mirceaulinic]

• Black-formatted the modules in 6f87b8c. (For future use, I've also added make black and make format in 63e96e4)
• In 88b2ca4 I've added Make instructions to make it easier to get started with, e.g.,

$ make mariadb
docker-compose -f docker/mariadb.yml up -d
Creating network "docker_default" with the default driver
Creating docker_mariadb_1 ... done
Creating docker_janitor_1 ... done

And the page should be available at http://localhost:8080/. In the Makefile, the image tag defaults to an image I've built in my own environment, and can override that with make mariadb IMAGE=<janitor image tag> after building using the Dockerfile from #3. We can later default to a publicly available Docker image once it'll be available on Docker hub.

Also can run make postgres with a similar effect, however there's a separate small issue we need to look into right now.

[mirceaulinic]

Pushed three more commits in the meanwhile, the most outstanding being 2f6bc87: remove the size restriction for the TEXT fields (checked against MariaDB and looks like it works with that).