The RSB documentation is now in ReST format and part of the RTEMS
Documentation project. See https://docs.rtems.org/.
Remove support for the GPL based asciidoc tool and remove the
asciidoc package from the RSB.
Add the Python Markdown package and update the reporter to use
Markdown for HTML generation. The resuling HTML report is a single
self contained file.
Closes#3047.
