Docker builds unmaintained and essentially broken

[JedMeister]

Marcos has highlighted that our Docker builds are broken and the website documentation does not result in a working TurnKey system. He has also provided some potential fixes which are greatly appreciated.

Our Docker builds really do need some love and be bought up to scratch. Unfortunately I'm not sure when we'll have some spare cycles, I have pinned this to the v19.x milestone, but obviously sooner would be better than later! So we'll see what we can do...