Generalize the copy_class to work with most of the str methods

argparse.py -
    __getattribute__ - apply the 'copy_class' action to methods
   _copy_class - return WSList
    WSList - _fill_text - return a Pre()

preformat.py - Hanging has its own copy_class and __getattribute__ to
   handle the extra header_indent attribute

try_12806_3.py - partial(Hanging, header_indent=6) working