LONDON (Reuters) – Should Eric Clapton ever decide to hang up the guitar, he might try his hand at art dealing. The 67-year-old British rocker is selling an abstract painting by German artist Gerhard Richter at Sotheby's next month which is expected to fetch $14-19 million. The price itself may raise barely an eyebrow in auction house circles, where Richter has long been one of the world's most sought after living painters with an auction record of $21.8 million set in New York in May. …