Fix Doc Scripts

* Fix bug where a section would be missing at end of converted md files
* Add a script to remove redundant section type names from converted MDs
* Add mdpretty script to make md files pretty after filtering
Add just-converted Markdown docs
Remove redundant headings from just-converted MDs

We are now in a position (hopefully!) to continue editing solely on the
Markdown documentation, but I will leave the original DocBook XML and
conversion scripts around for a while, just in case...