implementations for desctiption and debugDescription complete for all CoreStore types

Sources/ObjectiveC/CSGroupBy.swift

@@ -66,6 +66,11 @@ public final class CSGroupBy: NSObject, CSQueryClause, CoreStoreObjectiveCType {
         return self.bridgeToSwift == object.bridgeToSwift
     }
     
+    public override var description: String {
+        
+        return "(\(String(reflecting: self.dynamicType))) \(self.bridgeToSwift.coreStoreDumpString)"
+    }
+    
     
     // MARK: CSQueryClause