By Henry Burt Newcastle underlined their European football credentials on Saturday with an impressive 4-0 victory over Aston Villa at St. James’ Park. It was a stop-start first half, with lengthy stoppages required due to an injury to Villa goalkeeper Emiliano Martinez, who went down unchallenged shortly after catching a cross and had to be replaced by Robin Olsen. Olsen made a fantastic save shortly before half-time, but it was all for nought as moments later Newcastle were awarded a penalty when Ashley Young blocked Miguel Almiron’s shot with his hand. Callum Wilson smashed the penalty down …