By Renee Maltezou ATHENS, July 2 (Reuters) – Greece’s governing New Democracy party called on Thursday for its supporters to take to the streets in protest after the 72-year-old mother of one of its parliamentary candidates died of severe burns from a firebomb attack. Attackers placed flaming gas canisters at three homes of local figures from the governing party in the northern city of Thessaloniki before dawn on Tuesday, causing explosions.