修复bug和新增部分功能

RvAddinTest/RevitAddin.cs

@@ -127,7 +127,7 @@ public class RevitAddin : ExternalCommand
     {
         try
         {
-            var reference = UiDocument.Selection.PickObject(ObjectType.PointOnElement, new DwgBlockSelection(), "请选择dwg块");
+            var reference = UiDocument.Selection.PickObject(ObjectType.PointOnElement, new DwgBlockSelection(), "请选择dwg链接的块参照");
             var dwg = Document.GetElement(reference) as ImportInstance;
             var dwgTransform = dwg!.GetTotalTransform();