WIP: Convert all help files to markdown files in doc directory

This is a work in progress MR for: http://feedback.gitlab.com/forums/176466-general/suggestions/5507877-convert-all-help-files-to-markdown-files-in-doc-di

- [x] Workflow
- [ ] SSH Keys
- [x] Gitlab Markdown
- [ ] Permissions
- [ ] API
- [ ] Web Hooks
- [ ] Rake Tasks
- [ ] System Hooks
- [ ] Public Access
- [x] Security