* Add int8 GRU kernel with UTs

* Lint fixes

* More lint fixes

* temporally disable zero_copy

* add test

* follow comments

* fix calcu_gradients

* fix code place

* fix embedding interface usage

* support to_static(model)

* add warning and unittest

* Use the single GPU card to execute the test_fuse_bn_act_pass UT.

* add double grad for tile, test=develop

* add double grad for expand_v2 op, test=develop

* add double grad for expand, test=develop

* add some unittest cases ot verify jit.save, no_test

* add more unittests

* add test with example inputs

* polish implement details

* remove useless blank

* fix fetch random error

* parameter_server_optimizer support auto_strategy

 fix the CudaPinMemory bug for the equal op and add the test case for the equal op

Decrease the number of running iterations to reduce CI time.

CI system shows it decreased the unittest time from about 90 seconds to about 30 seconds

add lars to fleet meta optimizer

* refine launch and distributed repr string for print

* set default value to strategy in distributed_optimizer test=develop

* Add naming rule if not specific InputSpec.name

* fix function name typo

* refine comment

* remove print statement

* fix frobenius_norm error, rm p=0 2-axis support. test=develop

* fix summary rnn

* fix kl_div bug when input shape is [1] and reduction is batchmean

* enhance collect_op for dygraph, test=develop

* enhance detection ops with lod, test=develop

* support none bbox left in generate_proposals, test=develop

* unfiy MultiLevelRoisNum, test=develop

* update core.ops, test=develop

* add op register for new input & output, test=develop

* test=develop, add ps auto

* add correlation api to contrib

* fix weight

* fix weight and fix doc

* fix embeeding padding idx

* add UT

* fix interval

* delate some wrong message test=develop, test=document_fix

* delate some wrong message

* fix unsqueeze in dygraph

* add test

* add test

* fix typo for interp_v2,test=develop

* align with torch, test=develop

* add area mode, test=develop

* fix bug, test=develop

* format notes, test=develop

* update for converage, test=develop

* fix bilinear, test=develop

* fix bicubic, test=develop

* fix typo, test=develop

* fix coverage, test=develop

* fix helper.input_dtype, test=develop

* polish notes, test=develop

* polish notes, test=develop

* polish notes, test=develop