GitLab

* refactoring for losses

* update configs for guided anchoring

* add all imported losses to __all__

* allow weight=None for binary_cross_entropy

* use losses in mmdetection for FCOSHead

* bug fix for weight_reduce_loss

* add eps to iou_loss and handle weight=None

* unify loss api in FCOSHead

* fix avg_factor

* add cpp sigmoid focal loss

* modify interface

* format cpp code, support, fix pep8 error

* format cpp code as google style