* feat(platform): lazy initialization of devicecontext in pool

Use std::async(deferer, []{...}) to lazy initialize DeviceContext in Pool

test=develop

* Add future includes

test=develop

test=develop

Make all blob info saved in global device context to be thread based.
Meanwhile save thread id in thread local storage in ParallelDo

Add rpc profiler flags

test=develop

Add rpc timeline

test=develop

test=develop

test=develop

* profiler infor merge thread statistic information

* update profiler

* fix bug

* add merge thread msg to report

* optimize report

* statistic the time of ops in each thread but not all

* optimize report format

* optimize profile report

* optimize profile report
test=develop

test=develop

* flags

* "follow comment"

This reverts commit 1d91a49d.

* some trivial opt

* remove the fix of lod_tensor and shrink_rnn_memory_op

* refine ShrinkRNNMemoryOp

test=develop

* support test using executor without reader

* run imgnet

* update fluid benchmark

* wip

* update

* update all models

* support pyreader

* update

* clean up

* make profile batches contollable

* update API.spec

* update scripts

* clean dockerfile

* update

* clean comments

* add scope argument docstring

* use num_trainers to determine nccl init comms

This reverts commit 151e169e.