In a major blow to the National Association of Realtors and major real estate franchisors, hundreds of thousands of homesellers can ask to be reimbursed for more than $1 billion in commissions they paid to buyer agents in the past eight years as a result of a federal court ruling on Friday. The National Association of Realtors and real estate holding company Realogy on Monday both signaled plans to appeal the ruling. Just days after hearing oral arguments, Judge Stephen R. Bough of the U.S. District Court in Western Missouri granted class certification in one of two federal commissions lawsuits that could rock the real estate industry and impact how agents…