v1.1 model checkpoints

update weights

Pre-trained weights used by BoxTeacher

1. We modified detectron2 to ignore the model statedicts for teacher when loading official models, e.g., R-50 and R-101.
2. For third-party models, e.g., Swin-Transformer, we make a copy of the weights for both teacher and student, e.g., student.backbone.layer0.conv... and student.backbone.layer0.conv...