performace tunning

[Andrey1994]

subtasks:

• optimize memcpy from bindings to C part and back
• add support for gpu execution provider to onnx classifier #575
• optimize compilation process, check compilation options, etc
• improve docs for building with openmp
• better openmp support
• check that dependencies like kissfft are compiled properly with all available optimizations
• another look at Parallel signal processing algorithms #108
• refactor memory management in C# binding(too many memcpys)