Remove remaining traces of ReqIf support
- The ReqIF exporter is no longer supported, and also not accessible from the GUI anymore
- However, there are still code and documentation files with left-overs from the implementation that should be removed.
How to reproduce: Full-text search in workspace for “reqif”
(from redmine: issue id 3382, created on 2018-04-17, closed on 2018-05-08)