Feature/md reader

[Igmat]

Description of Change

Initial implementation for reader-md, some minor fixes (correct order for readers) and necessary changes for avoiding conflicts with existing plugins.

Pull Request check-list

• [x] Does the linter pass?
• [x] If this change fixes a bug (or a performance problem), is a regression test (or a benchmark) included?
• [x] Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?