Update mask demo docs, add model download from paddlehub

* [LITE][BM] support VGG,Inception,Mobilenet,Darknet, test=develop

* modify opt name test=develop

* fix code style test=develop

* test=develop

* replace gru RowWiseAdd Eigen with c implementation
test=develop

* update cuda doc. test=document_fix

* update for clang. test=document_fix

* [LITE][OPENCL] Add opencl image2d conv3x3. test=develop

* [DEMO] add mask detection demo, test=develop

* [DEMO] fix ssd detection demo bug, test=develop

* [LITE][OPENCL]Add scale kernel.

* [LITE][OPENCL]Add scale kernel, format code style.

add concat ut, test=develop

* fix axis compute, test=develop

* add other axis, test=develop

* fix ut. test=develop

* fix con+relu6/leakyRelu fusion in Fp32, test=develop

* note m=397 in sgemv_int8 ut, test=develop

* fix ios build error. test=develop

 fix conv_winograd multithreads bug 

* [ARM] add 5x5s2 depthwise conv armv8 impl, test=develop

* [ARM] add int8 5x5s2 dw conv armv7 impl, test=develop

* [ARM] add int8 5x5s2 dw conv impl, test=develop

* [ARM] close int8 conv ut, test=develop

[OPENCL] add sigmoid image2d kernel and ut

* fix: update fpga backend and kernel
test=develop

* style: style fix
test=develop

* Optimize the transform from Paddle' Tensor to EigenVector, avoiding defining multiple DDim.

* Optimize the compute implementation of several operators.
test=develop

* Optimize the InferShape of several operators.
test=develop

* Remove the new function, resize and CheckPositive in DDim.
test=develop

* Fix a bug in fc_op's InferShape.
test=develop

* update doc:add_operation, model_quantization and support_operation_list, test=document_fix

[LITE][OPENCL] Add 3 kernels of ElementwiseAdd/FusionElemenwiseAddAct op with opencl image format (#2844)

* [LITE][OPENCL] Add 3 kernels of ElementwiseAdd/FuseElementwiseAdd op. test=develop

test=develop

* [LITE][OPENCL][Image]develop 1x1/5x5/7x7 routing in conv_compute ,test=develop

* [LITE][OPENCL][Image]develop 1x1/5x5/7x7 routing in conv_compute ,convert bias filter in prepare for run ,test=develop

* [LITE][OPENCL] remove useless code. test=develop

* [LITE][OPENCL] finish 4 kernel and unit tests of image2d opencl elementwise_mul kernel. test=develop

* [LITE][OPENCL] Fix little bug of ASSERT. test=develop

* [LITE][OPENCL] Fix bug of channel_mul_d2 and d4. test=develop

* add docs

* FIX CXX DEMO MAKEFILE TO SUPPORT MAC COMPILE test=develop

* test=develop

* optimize quant_dequant_fuse_pass, test=develop

* update, test=develop

* update, test=develop

* fix bug for accessing the removed node, test=develop

* set the bias of int8 conv as float, test=develop

* support weight quantization, test=develop

* up, test=develop

* up, test=develop

* up, test=develop