By Suzanne McGee and Chris Prentice (Reuters) -The U.S. Securities and Exchange Commission on Monday paved the way for an asset manager to add exchange-traded share classes to mutual funds, a move expected to kick-start approvals for dozens of applicants, spark more ETFs and make the products more accessible to retail investors. The planned order, which is open for public response before the SEC moves ahead, is specific to Dimensional Fund Advisors and allows the asset management firm to launch the new s ...