Support imperative learning rate scheduler

* Add linear learning warmup method

This warmup lr can be combinated with other learning rate strategies.
For example:
            decayed_lr = fluid.layers.linear_lr_warmup(
                fluid.layers.piecewise_decay(boundaries, lr_steps),
                warmup_steps, start_lr, end_lr)

* fix cudnn batch norm accuracy test=develop

* fix cudnn batch norm accuracy test=develop

* disable failed test for later fix test=develop

Fix document array_read code error

remove the useless check 

* fix compiled
test=develop

* follow comments test=develop

KL div loss: add kldiv_loss op

Add attr 'axis' for softmax

Add temporal_shift op for TSM model

* Add DecoupledWeightDecay

remove profiling from int8 analyzer test

test=develop

test=develop

refine subgraph trt and anakin

* add slice support for dim < 0 test=develop

preprocess with PIL the full val dataset and save binary

create test for quantized resnet50

test=develop

test=develop

* fix comments of 16410, test=develop

* modify inplace_op_inference_test according to pass interface change, test=develop

test=develop

test=develop

test=develop

[slim]  Fix checkpoint of quantization strategy.

* Add a tool to summary model's PARAMS, FLOPs in paddle/fluid/contrib.

refine multiplex-doc 

move imperative to dygraph

test=develop

test=develop

* fuse optimizer

* Revert "[MKL-DNN] Fix to crash of Transformer when mkldnn is to be used (#16233)"

This reverts commit 13816dd4.
Apart from enabling transformer for MKL-DNN

* Revert "- MKL-DNN pooling updated to set_prim_desc"

This reverts commit c63f6b20.

Conflicts:
	paddle/fluid/operators/mkldnn/concat_mkldnn_op.cc

* Revert "[MKL-DNN] MKL-DNN specific Tensor modification (#15429)"

test=develop

This reverts commit dec9cf53.

* - concat compilation fix

- lint

test=develop

- Lint fixes

test=develop

- Lint fixes

test=develop

- Fix Transpose MKLDNN op

test=develop

Fix grad op makers

* fix threaded executor bug
test=develop

* change the order of class member
test=develop

* Fix Travis CI
test=develop

test=develop

Clean codes and fix some bugs.

refine trt first run
add quant dequant fuse pass
omit simplify_anakin_priorbox_detection template
omit transpose_flatten_concat_fuse template
test=develop

Revert "Fix allocator bug"