Add C++ Predictor class for inference

[kice]

Description

C++ Predictor class for easy inference

• Support quantized model

• Support non-float32 data input and output

Comments

Both c-predict-api and cpp-package are missing data type during copying. Please fix XD.

BTW, I can get around 2x performance by uint8 quantizing my model.

UPDATE: I tested uint8 quantization again, and I got about 2x more of GPU memory usage for uint8 quantized model and predit time is 4x longer than fp32 model.