ANKARA, July 6 (Reuters) - NATO Secretary General Mark Rutte said the right to hold demonstrations and media freedom were essential in democracies, when asked about Turkey’s recent crackdown on dissidents and restrictions ahead of this week’s summit. Turkey will host leaders from the 32 allied countries, as well as officials from NATO's partners, in Ankara for a summit on Tuesday and Wednesday. Authorities have stepped up security across the capital, banning demonstrations, erecting barricades a