Divide crop_size into crop_h and crop_w in transformer

[fslzj]

In many tasks, the height and width of image are not equal. When update caffe, I have to add the two parameter again. Can the two new parameter be added into next version? If crop_h and corp_w exists, crop_size will be ignored.

[lukeyeager]

FYI, it's been proposed before: BVLC#1980