By Euan Rocha TORONTO (Reuters) – BlackBerry Ltd said on Tuesday it bought a minority stake in privately held healthcare IT firm NantHealth, a move that offers a glimpse into the type of niche markets the smartphone maker is targeting as it attempts to engineer a turnaround. Waterloo, Ontario-based BlackBerry, a pioneer in the smartphone industry, has fallen on hard times as its market share has waned in recent years. …