As ubiquitous as bluegrass music is in modern-day New York City, sometimes it’s easy to forget about the greats who laid the groundwork for today’s lively scene. Last night at Jalopy, Brooklyn’s home for folk and roots music, Rick Snell (Mona’s Monday Night Bluegrass Session) paid tribute to the great Arthel Watson, otherwise known as Doc Watson, in a vibrant evening of diverse Doc Watson classics. Watson, who died in 2012, was known for his flat picking guitar style, but was