resolves #697 honor reftext defined in embedded section title anchor

- assign reftext defined in embedded anchor to section
- register id for block even if reftext and title are empty
- don't split on comma in reftext (only split on first comma)
disallow quoted values in block and inline anchors
Merge pull request #698 from mojavelinux/issue-697

resolves #697 honor reftext defined in embedded section title anchor