GitLab

* Add more documentation for the ops

* Add documentation for Faster R-CNN

* Add documentation for Mask R-CNN and Keypoint R-CNN

* Improve doc for RPN

* Add basic doc for GeneralizedRCNNTransform

* Lint fixes

* Add COCO pre-trained weights for Faster R-CNN R-50 FPN

* Add weights for Mask R-CNN and Keypoint R-CNN

* Split mask_rcnn.py into several files

* Lint