Fans of classical music had a light schedule last week, but there is plenty to be heard this week to make up for lost time. Most evenings it is going to come down to a choice. WEDNESDAY: >> The Embassy of Austria (3524 International Ct. NW) is hosting a series of concerts called An das Lied: Festival of Song 2007, devoted to the greats of German-language song composition. The music starts this Wednesday, with a…