stop using scope for \addtogroup. It was placing class methods into the
group documentation instead of the class documentation. The new style is
to explicitly tag the class as @ingroup. This new method will allow the
class to be linked in the group page, and the class page will contain
the detailed documentation of the class methods.
Should follow same path as FileHandle, although this is less used
and there is currently no route to introduce a hook for a customized
DirHandle in retarget.