Add Docker build / compose to prepare Mastodon Dev Env for vcr/cassette tests

[arittner]

We need a stable local mastodon instance to prepare vcr/cassette tests. The idea is to create a docker build script with python from the existing docker build script and create an own image with only the needed services and features. Maybe an own docker compose script is enough.

Anyway, the containers should be used to prepare new recorded cassette files.

The build process to do this, is a manual step for developers with the interest to contribute new functionality and tests.