LONDON (Reuters) – British musician and former Dire Straits frontman Mark Knopfler is selling off a large part of his extensive guitar collection at a London auction with part of the proceeds going to charity. The collection, which includes some of the most significant guitars from Knopfler’s 50-year career, is on show at Christie’s auction house ahead of the Jan. 31 sale. “It’s a wonderful collection of 122 items from Mark Knopfler spanning all of his career and it … represents physically his career as a musician and an instigator and supplier of our communal soundtrack,” Kerry Keane, Chris…