Add Easy Install Docs based on Ubuntu and Docker Compose

[mmattel]

Fixes: #807, #803, #775, #774

Added a new deployment example based on Ubuntu and docker compose. The example as been tested twice locally, full install and full removal, both successfully.

Currently visible on staging.

Language review necessary.

Backport to 5.0

[mmattel]

@tbsbdr with a lot of ongoing writing, I have renamed Basic Setup --> Test Setup.
That fits better into the follow up structure I am working on.

Ubuntu with Docker Compose
   Test Setup
   Server Setup
   Internet Access
   Deploy on Hetzner
   ...

[mmattel]

Putting this to draft to avoid accidentially merging.

[mmattel]

@phil-davis could you redo a language review? There has been text added respectively changed making this a good thing.