add more buttons; remove some sections covered in the docs; general c…

…leanup

- added dynamic buttons for packages/downloads which shows the latest version where possible
- dynamic next milestone buttons
- reordered to have package managers and docker on top, manual downloads afterwards
- remove the docker and the cli section, since they are covered equally in the docs + button links
- added more sections to the navigation, to find stuff easier
- dynamic go requirement version button
- some social media buttons
- general cleanup