* add stack op and its unit tests, test=develop

test=develop

* add x86 op and kernel : search_fc and sequence_topk_avg_pooling   for content-dnn model test=develop

* [X86] add attention_padding_mask op, x86 kernel and unit test

test=develop

* [CUDA] add attention_padding_mask cuda kernel and unit test

test=develop

- add var_conv_2d cuda kernel

- add var_conv_2d cuda kernel unit test

- temporarily set to two input mode, remove input(ROW) and input(COLUMN)

add search_group_padding op and x86 kernel

* [X86][CUDA] add sequence_arithmetic op , x86 kernel, cuda kernel and unit test

test=develop

* add sequence_arithmetic cuda kernel unit test

test=develop

* add search_seq_depadding x86 and cuda
* add match_matrix_tensor x86
* add search_grnn x86, no test

- add var_conv_2d op

- add var_conv_2d x86 kernel

- add var_conv_2d x86 test

* fix conv kernel bugs and open mobilenet ci test=develop

* update lookup_table arm x86, test=develop

* add lookup_table_v2_op for compatibility, test=develop

- add sequence_reverse op

- add sequence_reverse kernel for x86 and cuda

- add sequence_reverse_test for x86 and cuda

* add cast op for x86 platform

* alter the struct to class to hide the data and alter the pointer

- add sequence_concat op

- add sequence_concat kernel for x86 and cuda

- add sequence_concat_test for x86 and cuda

* update concat and unsqueeze, test=develop

update reshape op to support multiple input types of shape.
priority: input(ShapeTensor) > input(Shape) > attr(shape)

update slice op to support multiple iput types of starts and ends.
priority: input(StartsTensor) > input(StartsTensorList) > attr(starts)

* fix step rnn model run bugs test=develop

* add tanh op in x86 platform and its unittest, test=develop

* add gelu op on x86 platform and add its unittests, test=develop

* update depends for math_function for activation for gelu, test=develop

* make inceptionv4, resnet50, googlenet can run on x86 paltform and fix the compare part in x86 unittests, test=develop

* fix googlenet tests for benchmark record, test=develop

* [framework][profile] fix profile dump bug when op is feed and fetch test=develop (sangoly)

* enable pool2d op on x86 and add its unit tests, test=develop

* enable dropout op and add its unit tests, test=develop

* add tranpose, transpose2 op and add their unit tests, test=develop

enable conv2d op and its unit tests on x86 device

* fix bug for reshape op, test=develop

* fix asr modle related kernel bugs test=develop

* add full_api_static target and fix building errors, test=develop

* fix build errors, test=develop

* fix code style, test=develop

* fix lite/model_parser/pb/var_desc.cc, test=develop

* fix building errors, test=develop

* modify lite/tools/debug/CMakeLists.txt, test=develop

* add fill_constant_batch_size_like op and add its unittest

* add x86 gru&&relu&&sequence_expand_as op test=develop

add slice op, reshape op,  reshape2 op, squeeze op and squeeze2 op and their unittests for x86

* add lite x86 ops for ASR test=develop

* add lite x86 ops for ASR test=develop

* fix x86 ci run test problems test=develop

* fix mkl path for CI test=develop