Improve installation and deployment docs

[mosabua]

Currently this is all a bit of a mess. I think we have to structure it into separate sections for

• Installation overview, what options there are and such
• JAR installation
• Docker container usage (with docker compose)
• Helm chart usage
• Configuration, where it is the same for all of them
• Writing routing rules

and have requirements and such for each to some degree.

We also need to pull out the approaches for local testing .. maybe into separate sections or whatever.. and the stuff about building and using the locally built artifacts.

Its all a bit of a tangle at the moment so not sure how to best tackle this just yet.