Rinci/Riap-based command-line application framework

 Perinci::CmdLine is currently empty, because the implementation is currently
 split into Perinci::CmdLine::Lite (the lightweight version) and
 Perinci::CmdLine::Classic (the full but heavier version). There's also
 Perinci::CmdLine::Any that let's you choose between the two dynamically, à la
 Any::Moose. And finally there's also Perinci::CmdLine::Inline, the even more
 lightweight version.