more refactor in drcargs
more refactor in drcargs

 - rename some flags (but keep support for previous names)
 - use action=append for multi args
 - specify metavar for prettier usage messge

patmarion/director,mitdrc/director,patmarion/director,openhumanoids/director,manuelli/director,mitdrc/director,openhumanoids/director,manuelli/director,patmarion/director,mitdrc/director,manuelli/director,openhumanoids/director,mitdrc/director,manuelli/director,patmarion/director,mitdrc/director,patmarion/director,openhumanoids/director,manuelli/director,openhumanoids/director