Marat Khabibullin

Please add online hard example mining (OHEM) based on BCE, L1, L2 and other losses for binary classification. Loss = SumOfPositiveClassLosses / + alpha* SumOfNegativeClassLosses / + beta * SumOf**HARD**NegativeClassLosses...

Please support [Deformable convolution](https://arxiv.org/pdf/1703.06211.pdf) layer.