Unimplemented: `transA` and `transB` in `Gemm` layer

[lgxi24]

In fpgaConvNet, Gemm layer is implemented as InnerProductLayer. However, the main difference is that Gemm layer supports more parameters (Boolean flags transA, transB, scalars alpha, beta).

For the current model, all four parameters haven't been considered when the model is parsed from Onnx form to fpgaConvNet.