NSManager的一个简单demo,产生一多个随机数，然后可以撤销和恢复。-NSManager a simple demo, produces more than one random number, and then you can undo and redo.

常数边界: 所有新增边界像素使用一个常数，程序每0.5秒会产生一个随机数更新该常数值。 复制边界: 复制原图像的边界像素。- Constant boundary: use all boundary pixels of a new constant, every 0.5 seconds the program will generate a random number value of the constant update. Copy border: Copy the bounda