BERLIN,May20 (Xinhua) --GermanViceChancellorandEconomyMinisterPhilippRoeslersaidattheweekendthatEuropeanCommission'sagreementtobackaproposaltolevypunitivedutiesonChinesesolarpanelsisa"gravemistake." RoeslertoldWeltamSonntagnewspaperinaninterviewonSundaythatpunitivedutiesarethewronginstrumenttodealwiththedispute,addingt...