Instead of using Dockerfile for everything, we've introduced
a docker-compose.yml file and kept the Dockerfile to producing
a pure base image for the services defined.

docker-compose services:

- `mariadb` - Setup mariadb
- `sharness` - Run sharness suites
- `pytest-mysql` - Run pytest suites with MariaDB
- `pytest-sqlite` - Run pytest suites with SQLite
- `test` - Run all tests and produce a collective coverage report
    - This target mounts a cache volume and copies any successful
      coverage report back to `./cache/.coverage`. Users can run
      `./util/fix-coverage ./cache/.coverage` to rewrite source
      code paths and move coverage into place to view reports
      on your local system.

== Get Started ==

Build `aurweb:latest`.

    $ docker build -t aurweb:latest .

Run all tests via `docker-compose`.

    $ docker-compose up test

You can also purely run `pytest` in SQLite or MariaDB modes.

    $ docker-compose up pytest-sqlite
    $ docker-compose up pytest-mysql

Or `sharness` alone, which only uses SQLite internally.

    $ docker-compose up sharness

After running tests, coverage reports are stored in `./cache/.coverage`.
This database was most likely created in a different path, and so it
needs to be sanitized with `./util/fix-coverage`.

    $ ./util/fix-coverage cache/.coverage
    Copied coverage db to /path/to/aurweb/.coverage.
    $ coverage report
    ...
    $ coverage html
    $ coverage xml
    ...

Defined components:

**Entrypoints**

- mariadb-entrypoint.sh - setup mariadb and run its daemon
- test-mysql-entrypoint.sh - setup mysql configurations
- test-sqlite-entrypoint.sh - setup sqlite configurations
- tests-entrypoint.sh - setup mysql and sqlite configurations

**Scripts**

- run-mariadb.sh - setup databases
- run-pytests.sh - run pytest suites
- run-sharness.sh - run sharness suites
- run-tests.sh - run both pytests and sharness

**Health**

- mariadb.sh - A healthcheck script for the mariadb service
- pytest.sh - A healthcheck script for the pytest-* services
- sharness.sh - A healthcheck script for the sharness service

This Docker configuration is setup for tests, but should be
extendable for web and git servers.

**Changes to Makefile**

- Remove `.coverage` in the `clean` target
- Add a `coverage` target which prints a report and outputs xml

Signed-off-by: Kevin Morris <kevr@0cost.org>