Created by: heavengate

move train_batch_size sync from load_config to merge_config

synchronize batch_size only in load_config will work for ymls, but if specify batch size with -o TrainReader.batch_size=x, batch size specify by --opt will not synchronized, move sync code to merge_config to make sure batch_size is correctly synchronized. load_config will call merge_config to merge the yml config to global