The Museum of Socialist Art, Sofia   If it were not for the sculpture garden, who would ever come out to this dismal place, where long-poured concrete has been left to harden as parking lots and unleased office space? Yet come we do, hoping to unearth a brilliant gleam amidst the ashen waste, to prise out that object of uncommon worth— the relic that will brighten understanding. Yet should this dream-goal prove too demanding,   experience, close and coarse-grained, may suffice; we buy our tickets and head towards the yard. Set by the gate, as if to advertise some new…