wfxiang08

Results 2 issues of wfxiang08

1. 对cast.py进行了修改,增加了device参数,可以手动指定device; 2. 增加了Annocation的处理,保证包含Annotation的代码可以编译过 3. 添加了很多注释, 以及异常处理

Related issue: https://github.com/github/gh-ost/issues/483 ### Description `applyCopyRowsFunc` should be retriable. But when there is error, terminateRowIteration is called, which results in a panic. So terminateRowIteration should not be called inside applyCopyRowsFunc...