I felt the need to update the README for several reasons:

1. LDAP issues that the core maintainers team cannot really resolve
2. Cleaning up the somewhat messy structure near the end

The first point goes without explanantion. The second points includes:

2.1. The tagging convention is now easier to read and understand
2.2. Some bullut points or notes have been inlined to "stick" more to
     the content that it actually belongs to
2.3. The note about the "old" `setup.sh` for DMS `10.1.0` has been
     removed as it is obsolete now. We encourage users to upgrade to
     `10.4.0` anyways.
2.4. The markdown code highlighting is now using `CONSOLE` instead of
     `BASH` because `CONSOLE` is more appropriate.
2.5. Capitalized headings
2.6. Updated the section about `./setup.sh help` to be in one place now
     instead of two
2.7. DKIM key generation does now not interfere with user account
     creation.