OSLO, Norway — Norway began burying the dead on Friday, a week after an anti-immigrant extremist killed 76 people in a bombing and shooting rampage. Mourners of all ages vowed they would not let the massacre threaten their nation’s openness and democracy. An 18-year-old Muslim girl was the first victim to be laid to rest since the gunman opened fire at a political youth camp and bombed the government headquarters in Oslo. After a funeral service in the Nesodden church outside the capital, Bano Rashid, a Kurdish immigrant from Iraq, was buried in a Muslim rite.