Many projects, such as 'python-openstackclient', manually write
documentation for their cliff-based command line tools. In many cases,
this documentation is a 1:1 reflection of what one could build from the
command line. This is unnecessary overhead that could and should be
avoided.
Add an 'autoprogram-cliff' directive that will allow folks to
automatically document their command line tools.
Change-Id: I497e62382768ffc9668a103706001735a7d851ff
e7a6a596c5