[udesk/dante] Minor modification to danteRefObject.

Make danteRefObject return its argument for convenience.
This allows to simplify cases similar to:

DanteObject* obj = danteRefObject(data->d.some_object);
[udesk/dante] Fix indentation.
[udesk/dante] Fix indentation.
[udesk/dante] Make udeskFlush handle UDESK_HANDLE_NONE.

Flush every object in case of UDESK_HANDLE_NONE argument,
as specified in udesk.