Change release documentation and small fix to switcher script

[rloewe]

When reviewing this, you should also check the whole create_switcher.py script. The commit is not part of this pull request.

[rloewe]

I have fixed the issued mentioned in the code. I have also:

• Changed the default documentation to stable
• Added links to release specific documentation in release notes and templates
• Added a note about update README.md EasyBuild script in releasing documentation

I have not done anything about the latest tag. I felt that would be too time-consuming to fix in a good way.