Moscow (AFP) - Thousands rallied in central Moscow on Saturday to call on President Vladimir Putin not to stay in power indefinitely, in the first major protest by the Russian opposition since the Kremlin chief announced controversial plans to change the constitution.The rally marked five years since the assassination of opposition politician Boris Nemtsov but its organisers also want the event to send a message to Putin after he proposed major constitutional changes.Organisers, including the country's most prominent opposition leader Alexei Navalny, called for a mass turnout to show Putin tha...