Add docker-compose

[FoxxMD]

It's about time I made a production-ready one-click setup for CM.

CM can be run as-is, without docker-compose, because it uses sensible defaults and can generate dependencies as plain files (sqlite db) or use memory (memory cache) when none is provided.

However, to run in production, CM really should have proper databases and cache dependencies to in order to scale properly. DB should be mysql/postgres and cache should be Redis.

Additionally, adding (optional) reverse image/full text search would require elasticsearch as a dependency #101 without a substitute available.

A docker-compose file would make all these production dependencies available with one-click setup and I can make sure they are configured correctly.

[FoxxMD]

Implemented in e11a1d2