It happens more and more often that when we ask a set top provider what their best skill is, they reply software. That seems to be the case at ADB, the Swiss set top maker, which has just completed the tricky task of changing middleware, from the ancient Alcatel MiView to the Nangu TV platform at Telefonica O2 Czech Republic, without changing the actual set tops. The deal was first flagged in the Summer, when tiny local Czech supplier Nangu said it had won a contract to supply the next generation software. But that was probably underlined when in November Telefonica decided to sell its majority control in its Czech subsidiary to investment group PPF Group for €2.5 billion. The…