By Maureen Daly   Old Westbury Gardens hosted a sold-out inaugural luncheon honoring the legacy of Mary Phipps.   Mary’s vision and leadership helped shape the Old Westbury Gardens into the community treasure and nature park that it is today.   Old Westbury Gardens was the original home of the Phipps family - one of Old Westbury’s oldest and most notable families.    John and Margarita Phipps built the Westbury House in the early 1900s, reserving almost half of the grounds to