Remove unused files

This pull request is more of suggestion or food for discussion. It's about how clean the repository should be when it comes to unused files. For me, someone who hasn't worked on this code base for many years, the amount of files that may or may not be used somewhere in the build process is very confusing. To improve the code base, it's often better to remove files and code that are no longer in use. But I do understand the desire to keep previous work and that it's convenient to have reference material. Would it be an idea to create a new branch called "reference" where a copy of the current state is stored, and to clean the working repository by removing unused files?