Read extrusion tags for dimension entities

Dimension entities support DXF codes 210, 220, 230 and and DRW_Dimension
already had a extPoint member, but the tags were never used when
parsing.

src/libs/vdxf/libdxfrw/drw_entities.cpp

@@ -1097,6 +1097,15 @@ void DRW_Dimension::parseCode(int code, dxfReader *reader){
     case 51:
         hdir = reader->getDouble();
         break;
+    case 210:
+        extPoint.x = reader->getDouble();
+        break;
+    case 220:
+        extPoint.y = reader->getDouble();
+        break;
+    case 230:
+        extPoint.z = reader->getDouble();
+        break;
     default:
         DRW_Entity::parseCode(code, reader);
         break;