optparser: show optional option groups names in help messages
optparser: show optional option groups names in help messages

Change-Id: I63f2aeb837dd5f45ac0c03048e9e58d550981e8c
Reviewed-by: Tomasz Kotarba <8b3867507575202f48af38bb9127944ff4f4892a@morganstanley.com>
Tested-by: Aquilon Template Build testing and verification

quattor/aquilon,quattor/aquilon,quattor/aquilon