Encode bbox using anchor in the second stage

[kl456123]

For better optimization and better performance , use anchor encode bbox in the second stage like as the first stage instead of rois. But something needs to be noted here.

1. Is the anchor the same as that in the first stage ?( anchor consistence)
2. If not , how to do it ?( find the best anchor that has max iou with rois and their according gt box)