Folger Theatre’s “The Comedy of Errors” is a pure, unadulterated delight. From its clever frame to its charming onstage accompaniment provided by Jesse Terrill, it is a production that surprises and entertains from first moment to last. “The Comedy of Errors” is based on two plays by Roman playwright Plautus in which twin brothers, Antipholus of Syracuse and Antipholus of Ephesus, are separated by a storm at sea when they are very young. Their servants, Dromio of Syracuse and Dromio of Ephesus, are lost with them.