Help: Glob manual/*.rst in Sphinx configuration

Add the man page description line as explicit markup at the top of each
Help/manual/*.rst file and scan it from conf.py to automatically
generate the man_pages Sphinx configuration value.  This reduces the
number of places that need to be changed when a new manual is added.
Merge topic 'doc-conf-auto-manuals' into next

f88332f Help: Glob manual/*.rst in Sphinx configuration