yoda: add keyword hgroup for classifying options

Without this keyword options are clissified according to "for"-s.
Sometimes it is not enough, so hgroup can be used for fine-tuning.

Signed-off-by: Andrey Vagin <avagin@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@sacred.ru>
yoda: Check that boolean options don't have default-s and optarg-s

Signed-off-by: Pavel Emelyanov <xemul@sacred.ru>