NEW DELHI (Reuters) - Pakistan President Asif Ali Zardari will sit down to lunch with Indian Prime Minister Manmohan Singh in New Delhi on Sunday in the highest-level meeting on each other's soil in seven years as the nuclear-armed foes seek to normalize relations. Relations have warmed since Pakistan promised its neighbor most favored nation trade status in 2011, although a $10 million bounty offered by Washington for a Pakistani Islamist blamed for the 2008 attacks on Mumbai stirred old grievances. ...