* - update gru ff op Signed-off-by: Yurii <iuriish@yahoo.com> * - implementation and testing gru_bp op Signed-off-by: Yurii <iuriish@yahoo.com> * - neglect dependencies between dLdh/dLdhLast/dLdcLast in lstmLayer backprop Signed-off-by: Yurii <iuriish@yahoo.com>