批量图形操作，合并Undo

因为有好几个同学问到如何将多个图形操作步骤合并成一个Undo，所以就增加了比较实用的 combineRegen 函数。

• iOS 应用例(GiViewHelper *hlp)

  [hlp combineRegen:^{
      hlp.command = @"line{'points':[10,10, 20,20, 20,10, 30,20]}";
      hlp.command = @"lines{'points':[10,10, 20,20, 20,10, 30,20]}";
  }];
  

• Android 应用例(IViewHelper hlp)

  hlp.combineRegen(new Runnable() {
      @Override
      public void run() {
          hlp.setCommand("line{'points':[10,10, 20,20, 20,10, 30,20]}");
          hlp.setCommand("lines{'points':[10,10, 20,20, 20,10, 30,20]}");
      }
  });
  

• C# 应用例(WPFViewHelper hlp)

  hlp.CombineRegen(delegate()
  {
      hlp.Command = "line{'points':[10,10, 20,20, 20,10, 30,20]}";
      hlp.Command = "lines{'points':[10,10, 20,20, 20,10, 30,20]}";
  });