New Delhi, Sep 17 (UNI) Prime Minister Narendra Modi today thanked former President Ram Nath Kovind, former Vice President M Venkaiah Naidu and former Prime Minister H D Deve Gowda for their birthday greetings, using his responses to underline his stated emphasis on dignity, opportunity, empowerment and the collective efforts of citizens in building a prosperous and developed India. Modi, who turned 76 today, also expressed gratitude to people across the country for their messages, affection and blessings, saying the goodwill had given him "renewed strength" to continue serving the people. Responding to former President Ram Nath Kovind's greetings, he…