HOUSTON, Texas, March 19 -- The office of the U.S. Attorney for the Southern District of Texas issued the following news release: The former president of a Texas energy company has pleaded guilty to an illegal kickback scheme and a commodities insider trading scheme involving natural gas futures contracts. Matthew Clark, 56, Needville, entered his plea March 15, admitting he conspired with others to direct his employer's trades to Classic Energy LLC in exchange for illegal kickbacks. Specifica  more