Update and refactor readme (+ remove old .github folder)
The readme was outdated and not easy to read. I refactored it and removed/changed the obsolete parts. I didn't focus too much on the content, i think i will make another MR later on because a lot of stuff could still be improved.
- general refactoring of the readme
- toc improved and links added
- removed references to old FFS
- removed disclaimer at the beginning, since we are on gitlab now
- added reference to 'help needed' issues
- fixed some minor formatting issues
I also removed the .github file from the repo.