* add post training quantization and weight quantization docs

fix: move quant op to basic

skip fusing quantized conv2d + relu6 for now

Optimize cuda kernel and remove io_copy added by default due to missing fetch_cuda kernel

add multiclass_nms2 kernel, test=develop

* fix caliberate error, values from [-128, 127] to [-127, 127], test=develop
* add classify demo and detection demo, test=develop

* fix: update fpga doc
test=document_fix

* fix: update fpga doc & delete useless index.rst

* fix: update fpga md and index
     delete useless index.rst
     test=document_fix
     test=develop

* fix: add support_hardware md

* add weight quant for combined model after optimized, test=develop

* fix compile. test=develop

* fix: update fpga doc
test=document_fix

* fix: update fpga doc & delete useless index.rst

* fix: update fpga md and index
     delete useless index.rst
     test=document_fix
     test=develop

* add cv to index, test=develop, test=document_fix

* update support ops and kernels for release 2.3

* make full_publish to fix link bug in mask demo

add cv docs, test=document_fix

* Add reduce sum op test
test=develop

* add layout, opencl docs. test=document_fix

* fix link in doc. test=develop, test=document_fix

test=develop

* mobilenetv1/v2,mnasnet,yolonano,sr models passed with opencl image2d kernel. test=develop

* Fix gflag shape define. test=develop

* Replace Softsign Eigen with c implementation
test=develop

* Optimize softmax. When the input tensor is 2-D and axis is 1, there is no need to resize.

* Optimize the gru, avoid calling Tensor::Slice.
test=develop

* Remove a std::vector in softmax.
test=develop

* Define CalculateSeqWidth to get the width of a sequence.
test=develop