A former D.C. public school system principal pleaded guilty yesterday to taking more than $9,000 from a student fundraising account for personal purchases that included DVDs, lobster, sushi, calling cards and a Palm Pilot. Nae M. Davis, 58, former principal of John Burroughs Elementary School in Northeast, faces six months to two years in prison after pleading guilty to a felony theft charge, prosecutors said. Miss Davis, who will be sentenced next month in D.C. Superior Court, declined to comment yesterday when reached by phone at her home in the District. She said she was referring inquiries about the matter...