* allow sublayer or param shadow attrs

* add unittest
test=develop

* change remove fn name
test=develop

* add half_async in the communicator
* fix DistributedStrategy

* add learning rate api; test=develop

* fix uni test converage; test=develop

* fix travis ci error; test=develop

* fix comment; test=develop

* fix example error; test=develop

* polish the api description, test=develop
Co-authored-by: Nzhongpu <2013000149@qq.com>

* remove unused inputs, test=develop

* remove unused inputs, test=develop

* update dtype, test=develop

* remove unused inputs, test=develop

* update op_use_default_grad_op_maker, tese=develop

* resolve conflicts, test=develop

* follow comments, test=develop

* update center_loss_grad, test=develop

* Fixed warpctc, test=develop

* Set lod level of sequence_unpad's output to 1 in compile time

test=develop

* fix the en doc and example code of warpctc, test=develop, test=document_fix

* fix test_layers compare static graph and dygraph result; test=develop

* fix test_layers random error; test=develop

* add multiprocess for dygraph data loader, test=develop

* polish code & add safe gurad, test=develop

* refactor dygraph dataloader & add signal handler, test=develop

* fix member initializer compile error on ci, test=develop

* fix member initializer compile error one more, test=develop

* remove useless config, test=develop

* skip windows incompatible problem, test=develop

* add unittest for coverage, test=coverage

* add more exception unittest case, test=develop

* deal with signal handler coverage, test=develop

* polish code & add signal handler tests, test=develop

* deal with coverage ci problem, test=develop

* split data loader test & coverage ci fix, test=develop

* remove test_imperative_data_loader_with_exception, test=develop

* remove singal process except test case, test=develop

* add exception tests again & remove sample list test, test=develop

* split normal and exception unittests to diff class, test=develop

* polish doc for use_multiprocess effect in static mode, test=develop

修改了依赖lite的commit id：lite支持了var_conv_2d的级联使用

* add mul and matmul quantization, test=develop
* add test for matmul, test=develop

* DataParallel state dict don't include _layers.; test=develop

* add unitest of data parallel; test=develop

* add load state test; test=develop

* polish grad op check, test=develop, test=document_fix

* keep op_use_default_grad_maker.spec to avoid conflict, test=develop, test=document_fix

* remove _optimized_guard in dygrahpe_mode test=develop

* remove comment code test=develop

* remove list append test=develop

* remove list append test=develop

* polish regularization test=develop

* add comment of function test=develop

* rm name_scope in dygraph mode test=develop

* fix fsp_op, test=develop

* fix fsp grad op maker, test=develop

* update op_use_default_grad_op_maker.spec, test=develop

* fix save_dygraph with nonexistent dir
test=develop

* minor fix
test=develop

* fix unittest
test=develop

* fix static save
test=develop

* fix compile issue, test=develop

* force link libiomp5 when mklml is enabled, test=develop

enhanced ops: concat, nearest_interp, deformable_conv_v1, sequence_conv, transpose2, conv2d

* remove the useless third_party library from C++ inference library

* revert removing the install directory

* refine code, test=develop

* reuse contain_var, test=develop