Behind a tiny blue door with glass panels in Blackrock village in South Co Dublin hides one of Ireland’s fast-growing and most successful wealth managers.  Blacksheep Fund Management is squeezed between a jewellery shop and a clothing boutique. Neither pedestrians waiting at a bus stop outside or smokers loitering on the street outside the Wicked Wolf bar nearby take a second glance at it.  Its door is marked by a black sheep logo that looks like it might suit a graphic design firm. Yet, in fact, it represents a highly sophisticated business. It does not have a public website and…