Issues with Windows build

[tehtea]

Hello, I managed to get a converted model working using a Linux VM, but found two issues with the 0.2.6 .exe file when I tried doing the same thing in Windows 10:

1. No error messages shown when exceptions are thrown. To reproduce, download birealnet18.onnx and run onnx2bnn.exe birealnet18.onnx sample.dab --binary-convs 9000,
2. Converted models did not have the correct version number and thus could not be loaded into the Android app. To reproduce, run onnx2bnn.exe birealnet18.onnx sample.dab --aggressive and import sample.dab into the daBNN-example repository. An error message along the lines of E/libc++abi: terminating with uncaught exception of type std::runtime_error: model_->version() == 2 is not satisfied! The model version should be 2, got 2950774155 instead. should be shown in ADB Logcat.