checkpoint add initial inc/md2html.cfg file

Adjust HTML phase names and filenames under inc.

Improve phase documentation in inc/README.md.

Added inc/md2html.cfg as an initial markdown to HTML configuration
file.  The inc/md2html.cfg file is undergoing design evaluation and
thus may change.  Nevertheless the comments in inc/md2html.cfg give
some hints as to how HTML files will be formed from markdown files.

inc/sidenav.default.html

@@ -27,6 +27,5 @@
     <div class="sidenav">
       <a href="#top">Jump to top</a>
     </div>
-  </div>
 
 <!-- END: this line ends content from: /inc/sidenav.default.html -->